Inbox page-count gate + DataList/DropdownMenu primitives (#554)
* feat(inbox): skip AI extraction for multi-page PDFs (#553) Bedrock churns for minutes on multi-page PDFs (sales reports, bank statements, contracts) and returns nothing useful. Above 3 pages we now skip extraction entirely and mark the row with extraction_skipped=true; the document still lands in the inbox and can be attached or converted manually. Same gate applies to the /items/:id/attach path. Client can also opt out via skip_extraction=true (skip_reason=client_opt_out). The InvoiceInboxWorkspace renders an "Inte AI-tolkad" badge for skipped rows, distinct from the "Felaktig" failure state (status='error'). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * refactor(ui): introduce DataList + DropdownMenu primitives, roll out across list pages DataList replaces the per-row Card pattern across Granskning, Transactions, Invoices, Supplier invoices, and Pending. One bordered container with hairline rows matches the flat-with-hairlines aesthetic in CLAUDE.md — no shadows, no state-tinted borders, secondary token for selected/hover. DropdownMenu fills the gap for row-level action menus on TransactionInboxCard, TransactionHistoryList, and the page-level action menus on /transactions and /pending. Replaces ad-hoc Popover + buttons constructions. Migrates list pages and the transaction inbox/history components onto the new primitives. No behavior change beyond the visual unification. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * chore: add agent skills + gnubok domain skills, gitignore compliance reports .agents/skills/ + skills-lock.json + symlinks under .claude/skills/ check in the vercel-labs/agent-skills set pinned by the local skill manager (deploy-to-vercel, vercel-cli-with-tokens, react-best-practices, composition-patterns, react-native-skills, react-view-transitions, web-design-guidelines). Keeps the team on the same versions. .claude/skills/industry/ + .claude/skills/modifier/ are hand-authored vertical and entity-modifier skills for the specialized accountant agent — industries (konsult-it, e-handel, bygg-hantverk, reklambyra, saas-ai) and entity overlays (holding-ab, single-shareholder-ab-fmb, mixed- verksamhet). Project-owned content; lives in the repo by design. Also gitignores .compliance-reports/ — those are large generated SARIF/dossier artifacts from the compliance scanner. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * refactor(transactions): unify inbox/history chrome, drop swipe flow The transactions page mixed two-tier filtering, a swipe-view detour, and per-row Card chrome that didn't carry its weight. This pass collapses those into a single editorial-list surface and removes the unused swipe path entirely. User-visible changes: - Mode toggle (Att bokföra / Alla transaktioner) moved from a Tabs row under the header into a dropdown to the right of a unified search bar. Search now persists when switching modes. - Removed the swipe categorization view ("Gå igenom alla") and its trigger button. The 800-line SwipeCategorizationView component is deleted; suggestion-fetching shrinks to what the template picker still consumes. - Inbox rows now show one primary action: invoice/supplier-invoice match shortcut when auto-detected, else "Bokför". A new visible Link2 icon button opens the customer or supplier invoice picker manually (chosen by amount sign). Delete becomes a plain trash button — no overflow menu since it only ever held one item. - Bulk action bar swaps "Markera som privat" for "Ta bort" with a single combined confirmation. - Built SupplierInvoicePicker mirroring InvoicePicker so expense transactions can be matched to supplier invoices from the inbox. Wired through /api/transactions/{id}/match-supplier-invoice. - Template picker dialog renamed to "Bokför transaktion"; "Bokför manuellt…" and "Matcha med faktura…" promoted from muted ghost buttons at the bottom to outline buttons at the top, above the template list. - Breathing room: row padding py-3 → py-4, primary text text-sm → text-base, amount text-base, button heights h-8 → h-9, trailing gap-2 → gap-3 (in the DataList primitive itself, so every list benefits slightly). 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * fix: align package-lock.json with merged package.json The merge resolution took origin/main's package-lock.json (which dropped pdf-lib) but kept our package.json (which still requires pdf-lib for the invoice-inbox extension's PDFDocument import). `npm ci` rejected the mismatch. Regenerate the lock from the merged package.json so both files agree. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * fix: regenerate package-lock.json with npm@10 for CI compat Local npm@11 produced a lock that npm@10 (CI) rejected with "Missing: @swc/helpers@0.5.21". Regenerated with npm@10 --package-lock-only so CI can install. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * fix(transactions): supplier-invoice status-leak guard + drop dead prop Two follow-ups from the merge-risk audit: - SupplierInvoicePicker now mirrors InvoicePicker's status-leak guard: if a supplier invoice is still 'approved'/'overdue' but already has a payment voucher attached (journal_entry_id on supplier_invoice_payments), hide it. Closes a UX race window between payment and status flip. Partially-paid invoices still pass through. - Drop the unused onMarkPrivate prop on TransactionInboxCard and the matching handleMarkPrivate wrapper in the parent. Both became dead when the swipe-categorisation flow was removed. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Jakob Wennberg
@@ -0,0 +1,296 @@
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---
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name: deploy-to-vercel
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description: Deploy applications and websites to Vercel. Use when the user requests deployment actions like "deploy my app", "deploy and give me the link", "push this live", or "create a preview deployment".
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metadata:
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author: vercel
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version: "3.0.0"
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---
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# Deploy to Vercel
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Deploy any project to Vercel. **Always deploy as preview** (not production) unless the user explicitly asks for production.
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The goal is to get the user into the best long-term setup: their project linked to Vercel with git-push deploys. Every method below tries to move the user closer to that state.
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## Step 1: Gather Project State
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Run all four checks before deciding which method to use:
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```bash
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# 1. Check for a git remote
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git remote get-url origin 2>/dev/null
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# 2. Check if locally linked to a Vercel project (either file means linked)
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cat .vercel/project.json 2>/dev/null || cat .vercel/repo.json 2>/dev/null
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# 3. Check if the Vercel CLI is installed and authenticated
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vercel whoami 2>/dev/null
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# 4. List available teams (if authenticated)
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vercel teams list --format json 2>/dev/null
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```
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### Team selection
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If the user belongs to multiple teams, present all available team slugs as a bulleted list and ask which one to deploy to. Once the user picks a team, proceed immediately to the next step — do not ask for additional confirmation.
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Pass the team slug via `--scope` on all subsequent CLI commands (`vercel deploy`, `vercel link`, `vercel inspect`, etc.):
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```bash
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vercel deploy [path] -y --no-wait --scope <team-slug>
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```
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If the project is already linked (`.vercel/project.json` or `.vercel/repo.json` exists), the `orgId` in those files determines the team — no need to ask again. If there is only one team (or just a personal account), skip the prompt and use it directly.
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**About the `.vercel/` directory:** A linked project has either:
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- `.vercel/project.json` — created by `vercel link` (single project linking). Contains `projectId` and `orgId`.
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- `.vercel/repo.json` — created by `vercel link --repo` (repo-based linking). Contains `orgId`, `remoteName`, and a `projects` array mapping directories to Vercel project IDs.
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Either file means the project is linked. Check for both.
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**Do NOT** use `vercel project inspect`, `vercel ls`, or `vercel link` to detect state in an unlinked directory — without a `.vercel/` config, they will interactively prompt (or with `--yes`, silently link as a side-effect). Only `vercel whoami` is safe to run anywhere.
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## Step 2: Choose a Deploy Method
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### Linked (`.vercel/` exists) + has git remote → Git Push
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This is the ideal state. The project is linked and has git integration.
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1. **Ask the user before pushing.** Never push without explicit approval:
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```
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This project is connected to Vercel via git. I can commit and push to
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trigger a deployment. Want me to proceed?
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```
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2. **Commit and push:**
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```bash
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git add .
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git commit -m "deploy: <description of changes>"
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git push
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```
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Vercel automatically builds from the push. Non-production branches get preview deployments; the production branch (usually `main`) gets a production deployment.
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3. **Retrieve the preview URL.** If the CLI is authenticated:
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```bash
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sleep 5
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vercel ls --format json
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```
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The JSON output has a `deployments` array. Find the latest entry — its `url` field is the preview URL.
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If the CLI is not authenticated, tell the user to check the Vercel dashboard or the commit status checks on their git provider for the preview URL.
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---
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### Linked (`.vercel/` exists) + no git remote → `vercel deploy`
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The project is linked but there's no git repo. Deploy directly with the CLI.
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```bash
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vercel deploy [path] -y --no-wait
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```
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Use `--no-wait` so the CLI returns immediately with the deployment URL instead of blocking until the build finishes (builds can take a while). Then check on the deployment status with:
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```bash
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vercel inspect <deployment-url>
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```
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For production deploys (only if user explicitly asks):
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```bash
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vercel deploy [path] --prod -y --no-wait
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```
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---
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### Not linked + CLI is authenticated → Link first, then deploy
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The CLI is working but the project isn't linked yet. This is the opportunity to get the user into the best state.
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1. **Ask the user which team to deploy to.** Present the team slugs from Step 1 as a bulleted list. If there's only one team (or just a personal account), skip this step.
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2. **Once a team is selected, proceed directly to linking.** Tell the user what will happen but do not ask for separate confirmation:
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```
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Linking this project to <team name> on Vercel. This will create a Vercel
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project to deploy to and enable automatic deployments on future git pushes.
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```
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3. **If a git remote exists**, use repo-based linking with the selected team scope:
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```bash
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vercel link --repo --scope <team-slug>
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```
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This reads the git remote URL and matches it to existing Vercel projects that deploy from that repo. It creates `.vercel/repo.json`. This is much more reliable than `vercel link` (without `--repo`), which tries to match by directory name and often fails when the local folder and Vercel project are named differently.
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**If there is no git remote**, fall back to standard linking:
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```bash
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vercel link --scope <team-slug>
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```
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This prompts the user to select or create a project. It creates `.vercel/project.json`.
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4. **Then deploy using the best available method:**
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- If a git remote exists → commit and push (see git push method above)
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- If no git remote → `vercel deploy [path] -y --no-wait --scope <team-slug>`, then `vercel inspect <url>` to check status
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---
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### Not linked + CLI not authenticated → Install, auth, link, deploy
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The Vercel CLI isn't set up at all.
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1. **Install the CLI (if not already installed):**
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```bash
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npm install -g vercel
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```
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2. **Authenticate:**
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```bash
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vercel login
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```
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The user completes auth in their browser. If running in a non-interactive environment where login is not possible, skip to the **no-auth fallback** below.
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3. **Ask which team to deploy to** — present team slugs from `vercel teams list --format json` as a bulleted list. If only one team / personal account, skip. Once selected, proceed immediately.
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4. **Link the project** with the selected team scope (use `--repo` if a git remote exists, plain `vercel link` otherwise):
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```bash
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vercel link --repo --scope <team-slug> # if git remote exists
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vercel link --scope <team-slug> # if no git remote
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```
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5. **Deploy** using the best available method (git push if remote exists, otherwise `vercel deploy -y --no-wait --scope <team-slug>`, then `vercel inspect <url>` to check status).
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---
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### No-Auth Fallback — claude.ai sandbox
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**When to use:** Last resort when the CLI can't be installed or authenticated in the claude.ai sandbox. This requires no authentication — it returns a **Preview URL** (live site) and a **Claim URL** (transfer to your Vercel account).
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```bash
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bash /mnt/skills/user/deploy-to-vercel/resources/deploy.sh [path]
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```
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**Arguments:**
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- `path` - Directory to deploy, or a `.tgz` file (defaults to current directory)
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**Examples:**
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```bash
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# Deploy current directory
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bash /mnt/skills/user/deploy-to-vercel/resources/deploy.sh
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# Deploy specific project
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bash /mnt/skills/user/deploy-to-vercel/resources/deploy.sh /path/to/project
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# Deploy existing tarball
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bash /mnt/skills/user/deploy-to-vercel/resources/deploy.sh /path/to/project.tgz
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```
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The script auto-detects the framework from `package.json`, packages the project (excluding `node_modules`, `.git`, `.env`), uploads it, and waits for the build to complete.
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**Tell the user:** "Your deployment is ready at [previewUrl]. Claim it at [claimUrl] to manage your deployment."
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---
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### No-Auth Fallback — Codex sandbox
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**When to use:** In the Codex sandbox where the CLI may not be authenticated. Codex runs in a sandboxed environment by default — try the CLI first, and fall back to the deploy script if auth fails.
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1. **Check whether the Vercel CLI is installed** (no escalation needed for this check):
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```bash
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command -v vercel
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```
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2. **If `vercel` is installed**, try deploying with the CLI:
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```bash
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vercel deploy [path] -y --no-wait
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```
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3. **If `vercel` is not installed, or the CLI fails with "No existing credentials found"**, use the fallback script:
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```bash
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skill_dir="<path-to-skill>"
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# Deploy current directory
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bash "$skill_dir/resources/deploy-codex.sh"
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# Deploy specific project
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bash "$skill_dir/resources/deploy-codex.sh" /path/to/project
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# Deploy existing tarball
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bash "$skill_dir/resources/deploy-codex.sh" /path/to/project.tgz
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```
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The script handles framework detection, packaging, and deployment. It waits for the build to complete and returns JSON with `previewUrl` and `claimUrl`.
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**Tell the user:** "Your deployment is ready at [previewUrl]. Claim it at [claimUrl] to manage your deployment."
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**Escalated network access:** Only escalate the actual deploy command if sandboxing blocks the network call (`sandbox_permissions=require_escalated`). Do **not** escalate the `command -v vercel` check.
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---
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## Agent-Specific Notes
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### Claude Code / terminal-based agents
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You have full shell access. Do NOT use the `/mnt/skills/` path. Follow the decision flow above using the CLI directly.
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For the no-auth fallback, run the deploy script from the skill's installed location:
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```bash
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bash ~/.claude/skills/deploy-to-vercel/resources/deploy.sh [path]
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```
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The path may vary depending on where the user installed the skill.
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### Sandboxed environments (claude.ai)
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You likely cannot run `vercel login` or `git push`. Go directly to the **no-auth fallback — claude.ai sandbox**.
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### Codex
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Codex runs in a sandbox. Check if the CLI is available first, then fall back to the deploy script. Go to the **no-auth fallback — Codex sandbox**.
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---
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## Output
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Always show the user the deployment URL.
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- **Git push:** Use `vercel ls --format json` to find the preview URL. If the CLI isn't authenticated, tell the user to check the Vercel dashboard or commit status checks.
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- **CLI deploy:** Show the URL returned by `vercel deploy --no-wait`. Use `vercel inspect <url>` to check build status and report it to the user.
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||||
- **No-auth fallback:** Show both the preview URL and the claim URL:
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```
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Deployment successful!
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Preview URL: https://my-app-abc123.vercel.app
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Claim URL: https://vercel.com/claim-deployment?code=...
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||||
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View your site at the Preview URL.
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To transfer this deployment to your Vercel account, visit the Claim URL.
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```
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||||
**Do not** curl or fetch the deployed URL to verify it works. Just return the link.
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||||
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||||
---
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||||
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||||
## Troubleshooting
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||||
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||||
### Network Egress Error (claude.ai)
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||||
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||||
If deployment fails due to network restrictions on claude.ai, tell the user:
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||||
|
||||
```
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||||
Deployment failed due to network restrictions. To fix this:
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|
||||
1. Go to https://claude.ai/settings/capabilities
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2. Add *.vercel.com to the allowed domains
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3. Try deploying again
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```
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|
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### Escalated Network Access (Codex / sandboxed environments)
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|
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If deployment fails due to network issues (timeouts, DNS errors, connection resets) in a sandboxed environment, rerun with escalated permissions (`sandbox_permissions=require_escalated`). Do not escalate the initial CLI availability check — only escalate the actual deploy command.
|
||||
|
||||
Example guidance to the user:
|
||||
```
|
||||
The deploy needs escalated network access to deploy to Vercel. I can rerun
|
||||
the command with escalated permissions — want me to proceed?
|
||||
```
|
||||
|
||||
### CLI Auth Failure
|
||||
|
||||
If `vercel login` or `vercel deploy` fails with authentication errors, fall back to the no-auth deploy script (claude.ai or Codex variant, depending on the environment).
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||||
@@ -0,0 +1,301 @@
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#!/bin/bash
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# Vercel Deployment Script for Codex (via claimable deploy endpoint)
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# Usage: ./deploy-codex.sh [project-path]
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# Returns: JSON with previewUrl, claimUrl, deploymentId, projectId
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set -euo pipefail
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DEPLOY_ENDPOINT="https://codex-deploy-skills.vercel.sh/api/deploy"
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|
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# Detect framework from package.json
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detect_framework() {
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local pkg_json="$1"
|
||||
|
||||
if [ ! -f "$pkg_json" ]; then
|
||||
echo "null"
|
||||
return
|
||||
fi
|
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|
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local content=$(cat "$pkg_json")
|
||||
|
||||
# Helper to check if a package exists in dependencies or devDependencies.
|
||||
# Use exact matching by default, with a separate prefix matcher for scoped
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# package families like "@remix-run/".
|
||||
has_dep_exact() {
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||||
echo "$content" | grep -q "\"$1\""
|
||||
}
|
||||
|
||||
has_dep_prefix() {
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echo "$content" | grep -q "\"$1"
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}
|
||||
|
||||
# Order matters - check more specific frameworks first
|
||||
|
||||
# Blitz
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if has_dep_exact "blitz"; then echo "blitzjs"; return; fi
|
||||
|
||||
# Next.js
|
||||
if has_dep_exact "next"; then echo "nextjs"; return; fi
|
||||
|
||||
# Gatsby
|
||||
if has_dep_exact "gatsby"; then echo "gatsby"; return; fi
|
||||
|
||||
# Remix
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||||
if has_dep_prefix "@remix-run/"; then echo "remix"; return; fi
|
||||
|
||||
# React Router (v7 framework mode)
|
||||
if has_dep_prefix "@react-router/"; then echo "react-router"; return; fi
|
||||
|
||||
# TanStack Start
|
||||
if has_dep_exact "@tanstack/start"; then echo "tanstack-start"; return; fi
|
||||
|
||||
# Astro
|
||||
if has_dep_exact "astro"; then echo "astro"; return; fi
|
||||
|
||||
# Hydrogen (Shopify)
|
||||
if has_dep_exact "@shopify/hydrogen"; then echo "hydrogen"; return; fi
|
||||
|
||||
# SvelteKit
|
||||
if has_dep_exact "@sveltejs/kit"; then echo "sveltekit-1"; return; fi
|
||||
|
||||
# Svelte (standalone)
|
||||
if has_dep_exact "svelte"; then echo "svelte"; return; fi
|
||||
|
||||
# Nuxt
|
||||
if has_dep_exact "nuxt"; then echo "nuxtjs"; return; fi
|
||||
|
||||
# Vue with Vitepress
|
||||
if has_dep_exact "vitepress"; then echo "vitepress"; return; fi
|
||||
|
||||
# Vue with Vuepress
|
||||
if has_dep_exact "vuepress"; then echo "vuepress"; return; fi
|
||||
|
||||
# Gridsome
|
||||
if has_dep_exact "gridsome"; then echo "gridsome"; return; fi
|
||||
|
||||
# SolidStart
|
||||
if has_dep_exact "@solidjs/start"; then echo "solidstart-1"; return; fi
|
||||
|
||||
# Docusaurus
|
||||
if has_dep_exact "@docusaurus/core"; then echo "docusaurus-2"; return; fi
|
||||
|
||||
# RedwoodJS
|
||||
if has_dep_prefix "@redwoodjs/"; then echo "redwoodjs"; return; fi
|
||||
|
||||
# Hexo
|
||||
if has_dep_exact "hexo"; then echo "hexo"; return; fi
|
||||
|
||||
# Eleventy
|
||||
if has_dep_exact "@11ty/eleventy"; then echo "eleventy"; return; fi
|
||||
|
||||
# Angular / Ionic Angular
|
||||
if has_dep_exact "@ionic/angular"; then echo "ionic-angular"; return; fi
|
||||
if has_dep_exact "@angular/core"; then echo "angular"; return; fi
|
||||
|
||||
# Ionic React
|
||||
if has_dep_exact "@ionic/react"; then echo "ionic-react"; return; fi
|
||||
|
||||
# Create React App
|
||||
if has_dep_exact "react-scripts"; then echo "create-react-app"; return; fi
|
||||
|
||||
# Ember
|
||||
if has_dep_exact "ember-cli" || has_dep_exact "ember-source"; then echo "ember"; return; fi
|
||||
|
||||
# Dojo
|
||||
if has_dep_exact "@dojo/framework"; then echo "dojo"; return; fi
|
||||
|
||||
# Polymer
|
||||
if has_dep_prefix "@polymer/"; then echo "polymer"; return; fi
|
||||
|
||||
# Preact
|
||||
if has_dep_exact "preact"; then echo "preact"; return; fi
|
||||
|
||||
# Stencil
|
||||
if has_dep_exact "@stencil/core"; then echo "stencil"; return; fi
|
||||
|
||||
# UmiJS
|
||||
if has_dep_exact "umi"; then echo "umijs"; return; fi
|
||||
|
||||
# Sapper (legacy Svelte)
|
||||
if has_dep_exact "sapper"; then echo "sapper"; return; fi
|
||||
|
||||
# Saber
|
||||
if has_dep_exact "saber"; then echo "saber"; return; fi
|
||||
|
||||
# Sanity
|
||||
if has_dep_exact "sanity"; then echo "sanity-v3"; return; fi
|
||||
if has_dep_prefix "@sanity/"; then echo "sanity"; return; fi
|
||||
|
||||
# Storybook
|
||||
if has_dep_prefix "@storybook/"; then echo "storybook"; return; fi
|
||||
|
||||
# NestJS
|
||||
if has_dep_exact "@nestjs/core"; then echo "nestjs"; return; fi
|
||||
|
||||
# Elysia
|
||||
if has_dep_exact "elysia"; then echo "elysia"; return; fi
|
||||
|
||||
# Hono
|
||||
if has_dep_exact "hono"; then echo "hono"; return; fi
|
||||
|
||||
# Fastify
|
||||
if has_dep_exact "fastify"; then echo "fastify"; return; fi
|
||||
|
||||
# h3
|
||||
if has_dep_exact "h3"; then echo "h3"; return; fi
|
||||
|
||||
# Nitro
|
||||
if has_dep_exact "nitropack"; then echo "nitro"; return; fi
|
||||
|
||||
# Express
|
||||
if has_dep_exact "express"; then echo "express"; return; fi
|
||||
|
||||
# Vite (generic - check last among JS frameworks)
|
||||
if has_dep_exact "vite"; then echo "vite"; return; fi
|
||||
|
||||
# Parcel
|
||||
if has_dep_exact "parcel"; then echo "parcel"; return; fi
|
||||
|
||||
# No framework detected
|
||||
echo "null"
|
||||
}
|
||||
|
||||
# Parse arguments
|
||||
INPUT_PATH="${1:-.}"
|
||||
|
||||
# Create temp directory for packaging
|
||||
TEMP_DIR=$(mktemp -d)
|
||||
TARBALL="$TEMP_DIR/project.tgz"
|
||||
STAGING_DIR="$TEMP_DIR/staging"
|
||||
CLEANUP_TEMP=true
|
||||
|
||||
cleanup() {
|
||||
if [ "$CLEANUP_TEMP" = true ]; then
|
||||
rm -rf "$TEMP_DIR"
|
||||
fi
|
||||
}
|
||||
trap cleanup EXIT
|
||||
|
||||
echo "Preparing deployment..." >&2
|
||||
|
||||
# Check if input is a .tgz file or a directory
|
||||
FRAMEWORK="null"
|
||||
|
||||
if [ -f "$INPUT_PATH" ] && [[ "$INPUT_PATH" == *.tgz ]]; then
|
||||
# Input is already a tarball, use it directly
|
||||
echo "Using provided tarball..." >&2
|
||||
TARBALL="$INPUT_PATH"
|
||||
CLEANUP_TEMP=false
|
||||
# Can't detect framework from tarball, leave as null
|
||||
elif [ -d "$INPUT_PATH" ]; then
|
||||
# Input is a directory, need to tar it
|
||||
PROJECT_PATH=$(cd "$INPUT_PATH" && pwd)
|
||||
|
||||
# Detect framework from package.json
|
||||
FRAMEWORK=$(detect_framework "$PROJECT_PATH/package.json")
|
||||
|
||||
# Stage files into a temporary directory to avoid mutating the source tree.
|
||||
mkdir -p "$STAGING_DIR"
|
||||
echo "Staging project files..." >&2
|
||||
tar -C "$PROJECT_PATH" \
|
||||
--exclude='node_modules' \
|
||||
--exclude='.git' \
|
||||
--exclude='.env' \
|
||||
--exclude='.env.*' \
|
||||
-cf - . | tar -C "$STAGING_DIR" -xf -
|
||||
|
||||
# Check if this is a static HTML project (no package.json)
|
||||
if [ ! -f "$PROJECT_PATH/package.json" ]; then
|
||||
# Find HTML files in root
|
||||
HTML_FILES=$(find "$STAGING_DIR" -maxdepth 1 -name "*.html" -type f)
|
||||
HTML_COUNT=$(printf '%s\n' "$HTML_FILES" | sed '/^$/d' | wc -l | tr -d '[:space:]')
|
||||
|
||||
# If there's exactly one HTML file and it's not index.html, rename it
|
||||
if [ "$HTML_COUNT" -eq 1 ]; then
|
||||
HTML_FILE=$(echo "$HTML_FILES" | head -1)
|
||||
BASENAME=$(basename "$HTML_FILE")
|
||||
if [ "$BASENAME" != "index.html" ]; then
|
||||
echo "Renaming $BASENAME to index.html..." >&2
|
||||
mv "$HTML_FILE" "$STAGING_DIR/index.html"
|
||||
fi
|
||||
fi
|
||||
fi
|
||||
|
||||
# Create tarball from the staging directory
|
||||
echo "Creating deployment package..." >&2
|
||||
tar -czf "$TARBALL" -C "$STAGING_DIR" .
|
||||
else
|
||||
echo "Error: Input must be a directory or a .tgz file" >&2
|
||||
exit 1
|
||||
fi
|
||||
|
||||
if [ "$FRAMEWORK" != "null" ]; then
|
||||
echo "Detected framework: $FRAMEWORK" >&2
|
||||
fi
|
||||
|
||||
# Deploy
|
||||
echo "Deploying..." >&2
|
||||
RESPONSE=$(curl -s -X POST "$DEPLOY_ENDPOINT" -F "file=@$TARBALL" -F "framework=$FRAMEWORK")
|
||||
|
||||
# Check for error in response
|
||||
if echo "$RESPONSE" | grep -q '"error"'; then
|
||||
ERROR_MSG=$(echo "$RESPONSE" | grep -o '"error":"[^"]*"' | cut -d'"' -f4)
|
||||
echo "Error: $ERROR_MSG" >&2
|
||||
exit 1
|
||||
fi
|
||||
|
||||
# Extract URLs from response
|
||||
PREVIEW_URL=$(echo "$RESPONSE" | grep -o '"previewUrl":"[^"]*"' | cut -d'"' -f4)
|
||||
CLAIM_URL=$(echo "$RESPONSE" | grep -o '"claimUrl":"[^"]*"' | cut -d'"' -f4)
|
||||
|
||||
if [ -z "$PREVIEW_URL" ]; then
|
||||
echo "Error: Could not extract preview URL from response" >&2
|
||||
echo "$RESPONSE" >&2
|
||||
exit 1
|
||||
fi
|
||||
|
||||
echo "Deployment started. Waiting for build to complete..." >&2
|
||||
echo "Preview URL: $PREVIEW_URL" >&2
|
||||
|
||||
# Poll the preview URL until it returns a non-5xx response (5xx = still building)
|
||||
MAX_ATTEMPTS=60 # 5 minutes max (60 * 5 seconds)
|
||||
ATTEMPT=0
|
||||
|
||||
while [ $ATTEMPT -lt $MAX_ATTEMPTS ]; do
|
||||
HTTP_STATUS=$(curl -s -o /dev/null -w "%{http_code}" "$PREVIEW_URL")
|
||||
|
||||
if [ "$HTTP_STATUS" -eq 200 ]; then
|
||||
echo "" >&2
|
||||
echo "Deployment ready!" >&2
|
||||
break
|
||||
elif [ "$HTTP_STATUS" -ge 500 ]; then
|
||||
# 5xx means still building/deploying
|
||||
echo "Building... (attempt $((ATTEMPT + 1))/$MAX_ATTEMPTS)" >&2
|
||||
sleep 5
|
||||
ATTEMPT=$((ATTEMPT + 1))
|
||||
elif [ "$HTTP_STATUS" -ge 400 ] && [ "$HTTP_STATUS" -lt 500 ]; then
|
||||
# 4xx might be an error or the app itself returns 4xx - it's responding
|
||||
echo "" >&2
|
||||
echo "Deployment ready (returned $HTTP_STATUS)!" >&2
|
||||
break
|
||||
else
|
||||
# Any other status, assume it's ready
|
||||
echo "" >&2
|
||||
echo "Deployment ready!" >&2
|
||||
break
|
||||
fi
|
||||
done
|
||||
|
||||
if [ $ATTEMPT -eq $MAX_ATTEMPTS ]; then
|
||||
echo "" >&2
|
||||
echo "Warning: Timed out waiting for deployment, but it may still be building." >&2
|
||||
fi
|
||||
|
||||
echo "" >&2
|
||||
echo "Preview URL: $PREVIEW_URL" >&2
|
||||
echo "Claim URL: $CLAIM_URL" >&2
|
||||
echo "" >&2
|
||||
|
||||
# Output JSON for programmatic use
|
||||
echo "$RESPONSE"
|
||||
@@ -0,0 +1,301 @@
|
||||
#!/bin/bash
|
||||
|
||||
# Vercel Deployment Script (via claimable deploy endpoint)
|
||||
# Usage: ./deploy.sh [project-path]
|
||||
# Returns: JSON with previewUrl, claimUrl, deploymentId, projectId
|
||||
|
||||
set -euo pipefail
|
||||
|
||||
DEPLOY_ENDPOINT="https://claude-skills-deploy.vercel.com/api/deploy"
|
||||
|
||||
# Detect framework from package.json
|
||||
detect_framework() {
|
||||
local pkg_json="$1"
|
||||
|
||||
if [ ! -f "$pkg_json" ]; then
|
||||
echo "null"
|
||||
return
|
||||
fi
|
||||
|
||||
local content=$(cat "$pkg_json")
|
||||
|
||||
# Helper to check if a package exists in dependencies or devDependencies.
|
||||
# Use exact matching by default, with a separate prefix matcher for scoped
|
||||
# package families like "@remix-run/".
|
||||
has_dep_exact() {
|
||||
echo "$content" | grep -q "\"$1\""
|
||||
}
|
||||
|
||||
has_dep_prefix() {
|
||||
echo "$content" | grep -q "\"$1"
|
||||
}
|
||||
|
||||
# Order matters - check more specific frameworks first
|
||||
|
||||
# Blitz
|
||||
if has_dep_exact "blitz"; then echo "blitzjs"; return; fi
|
||||
|
||||
# Next.js
|
||||
if has_dep_exact "next"; then echo "nextjs"; return; fi
|
||||
|
||||
# Gatsby
|
||||
if has_dep_exact "gatsby"; then echo "gatsby"; return; fi
|
||||
|
||||
# Remix
|
||||
if has_dep_prefix "@remix-run/"; then echo "remix"; return; fi
|
||||
|
||||
# React Router (v7 framework mode)
|
||||
if has_dep_prefix "@react-router/"; then echo "react-router"; return; fi
|
||||
|
||||
# TanStack Start
|
||||
if has_dep_exact "@tanstack/start"; then echo "tanstack-start"; return; fi
|
||||
|
||||
# Astro
|
||||
if has_dep_exact "astro"; then echo "astro"; return; fi
|
||||
|
||||
# Hydrogen (Shopify)
|
||||
if has_dep_exact "@shopify/hydrogen"; then echo "hydrogen"; return; fi
|
||||
|
||||
# SvelteKit
|
||||
if has_dep_exact "@sveltejs/kit"; then echo "sveltekit-1"; return; fi
|
||||
|
||||
# Svelte (standalone)
|
||||
if has_dep_exact "svelte"; then echo "svelte"; return; fi
|
||||
|
||||
# Nuxt
|
||||
if has_dep_exact "nuxt"; then echo "nuxtjs"; return; fi
|
||||
|
||||
# Vue with Vitepress
|
||||
if has_dep_exact "vitepress"; then echo "vitepress"; return; fi
|
||||
|
||||
# Vue with Vuepress
|
||||
if has_dep_exact "vuepress"; then echo "vuepress"; return; fi
|
||||
|
||||
# Gridsome
|
||||
if has_dep_exact "gridsome"; then echo "gridsome"; return; fi
|
||||
|
||||
# SolidStart
|
||||
if has_dep_exact "@solidjs/start"; then echo "solidstart-1"; return; fi
|
||||
|
||||
# Docusaurus
|
||||
if has_dep_exact "@docusaurus/core"; then echo "docusaurus-2"; return; fi
|
||||
|
||||
# RedwoodJS
|
||||
if has_dep_prefix "@redwoodjs/"; then echo "redwoodjs"; return; fi
|
||||
|
||||
# Hexo
|
||||
if has_dep_exact "hexo"; then echo "hexo"; return; fi
|
||||
|
||||
# Eleventy
|
||||
if has_dep_exact "@11ty/eleventy"; then echo "eleventy"; return; fi
|
||||
|
||||
# Angular / Ionic Angular
|
||||
if has_dep_exact "@ionic/angular"; then echo "ionic-angular"; return; fi
|
||||
if has_dep_exact "@angular/core"; then echo "angular"; return; fi
|
||||
|
||||
# Ionic React
|
||||
if has_dep_exact "@ionic/react"; then echo "ionic-react"; return; fi
|
||||
|
||||
# Create React App
|
||||
if has_dep_exact "react-scripts"; then echo "create-react-app"; return; fi
|
||||
|
||||
# Ember
|
||||
if has_dep_exact "ember-cli" || has_dep_exact "ember-source"; then echo "ember"; return; fi
|
||||
|
||||
# Dojo
|
||||
if has_dep_exact "@dojo/framework"; then echo "dojo"; return; fi
|
||||
|
||||
# Polymer
|
||||
if has_dep_prefix "@polymer/"; then echo "polymer"; return; fi
|
||||
|
||||
# Preact
|
||||
if has_dep_exact "preact"; then echo "preact"; return; fi
|
||||
|
||||
# Stencil
|
||||
if has_dep_exact "@stencil/core"; then echo "stencil"; return; fi
|
||||
|
||||
# UmiJS
|
||||
if has_dep_exact "umi"; then echo "umijs"; return; fi
|
||||
|
||||
# Sapper (legacy Svelte)
|
||||
if has_dep_exact "sapper"; then echo "sapper"; return; fi
|
||||
|
||||
# Saber
|
||||
if has_dep_exact "saber"; then echo "saber"; return; fi
|
||||
|
||||
# Sanity
|
||||
if has_dep_exact "sanity"; then echo "sanity-v3"; return; fi
|
||||
if has_dep_prefix "@sanity/"; then echo "sanity"; return; fi
|
||||
|
||||
# Storybook
|
||||
if has_dep_prefix "@storybook/"; then echo "storybook"; return; fi
|
||||
|
||||
# NestJS
|
||||
if has_dep_exact "@nestjs/core"; then echo "nestjs"; return; fi
|
||||
|
||||
# Elysia
|
||||
if has_dep_exact "elysia"; then echo "elysia"; return; fi
|
||||
|
||||
# Hono
|
||||
if has_dep_exact "hono"; then echo "hono"; return; fi
|
||||
|
||||
# Fastify
|
||||
if has_dep_exact "fastify"; then echo "fastify"; return; fi
|
||||
|
||||
# h3
|
||||
if has_dep_exact "h3"; then echo "h3"; return; fi
|
||||
|
||||
# Nitro
|
||||
if has_dep_exact "nitropack"; then echo "nitro"; return; fi
|
||||
|
||||
# Express
|
||||
if has_dep_exact "express"; then echo "express"; return; fi
|
||||
|
||||
# Vite (generic - check last among JS frameworks)
|
||||
if has_dep_exact "vite"; then echo "vite"; return; fi
|
||||
|
||||
# Parcel
|
||||
if has_dep_exact "parcel"; then echo "parcel"; return; fi
|
||||
|
||||
# No framework detected
|
||||
echo "null"
|
||||
}
|
||||
|
||||
# Parse arguments
|
||||
INPUT_PATH="${1:-.}"
|
||||
|
||||
# Create temp directory for packaging
|
||||
TEMP_DIR=$(mktemp -d)
|
||||
TARBALL="$TEMP_DIR/project.tgz"
|
||||
STAGING_DIR="$TEMP_DIR/staging"
|
||||
CLEANUP_TEMP=true
|
||||
|
||||
cleanup() {
|
||||
if [ "$CLEANUP_TEMP" = true ]; then
|
||||
rm -rf "$TEMP_DIR"
|
||||
fi
|
||||
}
|
||||
trap cleanup EXIT
|
||||
|
||||
echo "Preparing deployment..." >&2
|
||||
|
||||
# Check if input is a .tgz file or a directory
|
||||
FRAMEWORK="null"
|
||||
|
||||
if [ -f "$INPUT_PATH" ] && [[ "$INPUT_PATH" == *.tgz ]]; then
|
||||
# Input is already a tarball, use it directly
|
||||
echo "Using provided tarball..." >&2
|
||||
TARBALL="$INPUT_PATH"
|
||||
CLEANUP_TEMP=false
|
||||
# Can't detect framework from tarball, leave as null
|
||||
elif [ -d "$INPUT_PATH" ]; then
|
||||
# Input is a directory, need to tar it
|
||||
PROJECT_PATH=$(cd "$INPUT_PATH" && pwd)
|
||||
|
||||
# Detect framework from package.json
|
||||
FRAMEWORK=$(detect_framework "$PROJECT_PATH/package.json")
|
||||
|
||||
# Stage files into a temporary directory to avoid mutating the source tree.
|
||||
mkdir -p "$STAGING_DIR"
|
||||
echo "Staging project files..." >&2
|
||||
tar -C "$PROJECT_PATH" \
|
||||
--exclude='node_modules' \
|
||||
--exclude='.git' \
|
||||
--exclude='.env' \
|
||||
--exclude='.env.*' \
|
||||
-cf - . | tar -C "$STAGING_DIR" -xf -
|
||||
|
||||
# Check if this is a static HTML project (no package.json)
|
||||
if [ ! -f "$PROJECT_PATH/package.json" ]; then
|
||||
# Find HTML files in root
|
||||
HTML_FILES=$(find "$STAGING_DIR" -maxdepth 1 -name "*.html" -type f)
|
||||
HTML_COUNT=$(printf '%s\n' "$HTML_FILES" | sed '/^$/d' | wc -l | tr -d '[:space:]')
|
||||
|
||||
# If there's exactly one HTML file and it's not index.html, rename it
|
||||
if [ "$HTML_COUNT" -eq 1 ]; then
|
||||
HTML_FILE=$(echo "$HTML_FILES" | head -1)
|
||||
BASENAME=$(basename "$HTML_FILE")
|
||||
if [ "$BASENAME" != "index.html" ]; then
|
||||
echo "Renaming $BASENAME to index.html..." >&2
|
||||
mv "$HTML_FILE" "$STAGING_DIR/index.html"
|
||||
fi
|
||||
fi
|
||||
fi
|
||||
|
||||
# Create tarball from the staging directory
|
||||
echo "Creating deployment package..." >&2
|
||||
tar -czf "$TARBALL" -C "$STAGING_DIR" .
|
||||
else
|
||||
echo "Error: Input must be a directory or a .tgz file" >&2
|
||||
exit 1
|
||||
fi
|
||||
|
||||
if [ "$FRAMEWORK" != "null" ]; then
|
||||
echo "Detected framework: $FRAMEWORK" >&2
|
||||
fi
|
||||
|
||||
# Deploy
|
||||
echo "Deploying..." >&2
|
||||
RESPONSE=$(curl -s -X POST "$DEPLOY_ENDPOINT" -F "file=@$TARBALL" -F "framework=$FRAMEWORK")
|
||||
|
||||
# Check for error in response
|
||||
if echo "$RESPONSE" | grep -q '"error"'; then
|
||||
ERROR_MSG=$(echo "$RESPONSE" | grep -o '"error":"[^"]*"' | cut -d'"' -f4)
|
||||
echo "Error: $ERROR_MSG" >&2
|
||||
exit 1
|
||||
fi
|
||||
|
||||
# Extract URLs from response
|
||||
PREVIEW_URL=$(echo "$RESPONSE" | grep -o '"previewUrl":"[^"]*"' | cut -d'"' -f4)
|
||||
CLAIM_URL=$(echo "$RESPONSE" | grep -o '"claimUrl":"[^"]*"' | cut -d'"' -f4)
|
||||
|
||||
if [ -z "$PREVIEW_URL" ]; then
|
||||
echo "Error: Could not extract preview URL from response" >&2
|
||||
echo "$RESPONSE" >&2
|
||||
exit 1
|
||||
fi
|
||||
|
||||
echo "Deployment started. Waiting for build to complete..." >&2
|
||||
echo "Preview URL: $PREVIEW_URL" >&2
|
||||
|
||||
# Poll the preview URL until it returns a non-5xx response (5xx = still building)
|
||||
MAX_ATTEMPTS=60 # 5 minutes max (60 * 5 seconds)
|
||||
ATTEMPT=0
|
||||
|
||||
while [ $ATTEMPT -lt $MAX_ATTEMPTS ]; do
|
||||
HTTP_STATUS=$(curl -s -o /dev/null -w "%{http_code}" "$PREVIEW_URL")
|
||||
|
||||
if [ "$HTTP_STATUS" -eq 200 ]; then
|
||||
echo "" >&2
|
||||
echo "Deployment ready!" >&2
|
||||
break
|
||||
elif [ "$HTTP_STATUS" -ge 500 ]; then
|
||||
# 5xx means still building/deploying
|
||||
echo "Building... (attempt $((ATTEMPT + 1))/$MAX_ATTEMPTS)" >&2
|
||||
sleep 5
|
||||
ATTEMPT=$((ATTEMPT + 1))
|
||||
elif [ "$HTTP_STATUS" -ge 400 ] && [ "$HTTP_STATUS" -lt 500 ]; then
|
||||
# 4xx might be an error or the app itself returns 4xx - it's responding
|
||||
echo "" >&2
|
||||
echo "Deployment ready (returned $HTTP_STATUS)!" >&2
|
||||
break
|
||||
else
|
||||
# Any other status, assume it's ready
|
||||
echo "" >&2
|
||||
echo "Deployment ready!" >&2
|
||||
break
|
||||
fi
|
||||
done
|
||||
|
||||
if [ $ATTEMPT -eq $MAX_ATTEMPTS ]; then
|
||||
echo "" >&2
|
||||
echo "Warning: Timed out waiting for deployment, but it may still be building." >&2
|
||||
fi
|
||||
|
||||
echo "" >&2
|
||||
echo "Preview URL: $PREVIEW_URL" >&2
|
||||
echo "Claim URL: $CLAIM_URL" >&2
|
||||
echo "" >&2
|
||||
|
||||
# Output JSON for programmatic use
|
||||
echo "$RESPONSE"
|
||||
@@ -0,0 +1,353 @@
|
||||
---
|
||||
name: vercel-cli-with-tokens
|
||||
description: Deploy and manage projects on Vercel using token-based authentication. Use when working with Vercel CLI using access tokens rather than interactive login — e.g. "deploy to vercel", "set up vercel", "add environment variables to vercel".
|
||||
metadata:
|
||||
author: vercel
|
||||
version: "1.0.0"
|
||||
---
|
||||
|
||||
# Vercel CLI with Tokens
|
||||
|
||||
Deploy and manage projects on Vercel using the CLI with token-based authentication, without relying on `vercel login`.
|
||||
|
||||
## Step 1: Locate the Vercel Token
|
||||
|
||||
Before running any Vercel CLI commands, identify where the token is coming from. Work through these scenarios in order:
|
||||
|
||||
### A) `VERCEL_TOKEN` is already set in the environment
|
||||
|
||||
```bash
|
||||
printenv VERCEL_TOKEN
|
||||
```
|
||||
|
||||
If this returns a value, you're ready. Skip to Step 2.
|
||||
|
||||
### B) Token is in a `.env` file under `VERCEL_TOKEN`
|
||||
|
||||
```bash
|
||||
grep '^VERCEL_TOKEN=' .env 2>/dev/null
|
||||
```
|
||||
|
||||
If found, export it:
|
||||
|
||||
```bash
|
||||
export VERCEL_TOKEN=$(grep '^VERCEL_TOKEN=' .env | cut -d= -f2-)
|
||||
```
|
||||
|
||||
### C) Token is in a `.env` file under a different name
|
||||
|
||||
Look for any variable that looks like a Vercel token (Vercel tokens typically start with `vca_`):
|
||||
|
||||
```bash
|
||||
grep -i 'vercel' .env 2>/dev/null
|
||||
```
|
||||
|
||||
Inspect the output to identify which variable holds the token, then export it as `VERCEL_TOKEN`:
|
||||
|
||||
```bash
|
||||
export VERCEL_TOKEN=$(grep '^<VARIABLE_NAME>=' .env | cut -d= -f2-)
|
||||
```
|
||||
|
||||
### D) No token found — ask the user
|
||||
|
||||
If none of the above yield a token, ask the user to provide one. They can create a Vercel access token at vercel.com/account/tokens.
|
||||
|
||||
---
|
||||
|
||||
**Important:** Once `VERCEL_TOKEN` is exported as an environment variable, the Vercel CLI reads it natively — **do not pass it as a `--token` flag**. Putting secrets in command-line arguments exposes them in shell history and process listings.
|
||||
|
||||
```bash
|
||||
# Bad — token visible in shell history and process listings
|
||||
vercel deploy --token "vca_abc123"
|
||||
|
||||
# Good — CLI reads VERCEL_TOKEN from the environment
|
||||
export VERCEL_TOKEN="vca_abc123"
|
||||
vercel deploy
|
||||
```
|
||||
|
||||
## Step 2: Locate the Project and Team
|
||||
|
||||
Similarly, check for the project ID and team scope. These let the CLI target the right project without needing `vercel link`.
|
||||
|
||||
```bash
|
||||
# Check environment
|
||||
printenv VERCEL_PROJECT_ID
|
||||
printenv VERCEL_ORG_ID
|
||||
|
||||
# Or check .env
|
||||
grep -i 'vercel' .env 2>/dev/null
|
||||
```
|
||||
|
||||
**If you have a project URL** (e.g. `https://vercel.com/my-team/my-project`), extract the team slug:
|
||||
|
||||
```bash
|
||||
# e.g. "my-team" from "https://vercel.com/my-team/my-project"
|
||||
echo "$PROJECT_URL" | sed 's|https://vercel.com/||' | cut -d/ -f1
|
||||
```
|
||||
|
||||
**If you have both `VERCEL_ORG_ID` and `VERCEL_PROJECT_ID` in your environment**, export them — the CLI will use these automatically and skip any `.vercel/` directory:
|
||||
|
||||
```bash
|
||||
export VERCEL_ORG_ID="<org-id>"
|
||||
export VERCEL_PROJECT_ID="<project-id>"
|
||||
```
|
||||
|
||||
Note: `VERCEL_ORG_ID` and `VERCEL_PROJECT_ID` must be set together — setting only one causes an error.
|
||||
|
||||
## CLI Setup
|
||||
|
||||
Ensure the Vercel CLI is installed and up to date:
|
||||
|
||||
```bash
|
||||
npm install -g vercel
|
||||
vercel --version
|
||||
```
|
||||
|
||||
## Deploying a Project
|
||||
|
||||
Always deploy as **preview** unless the user explicitly requests production. Choose a method based on what you have available.
|
||||
|
||||
### Quick Deploy (have project ID — no linking needed)
|
||||
|
||||
When `VERCEL_TOKEN` and `VERCEL_PROJECT_ID` are set in the environment, deploy directly:
|
||||
|
||||
```bash
|
||||
vercel deploy -y --no-wait
|
||||
```
|
||||
|
||||
With a team scope (either via `VERCEL_ORG_ID` or `--scope`):
|
||||
|
||||
```bash
|
||||
vercel deploy --scope <team-slug> -y --no-wait
|
||||
```
|
||||
|
||||
Production (only when explicitly requested):
|
||||
|
||||
```bash
|
||||
vercel deploy --prod --scope <team-slug> -y --no-wait
|
||||
```
|
||||
|
||||
Check status:
|
||||
|
||||
```bash
|
||||
vercel inspect <deployment-url>
|
||||
```
|
||||
|
||||
### Full Deploy Flow (no project ID — need to link)
|
||||
|
||||
Use this when you have a token and team but no pre-existing project ID.
|
||||
|
||||
#### Check project state first
|
||||
|
||||
```bash
|
||||
# Does the project have a git remote?
|
||||
git remote get-url origin 2>/dev/null
|
||||
|
||||
# Is it already linked to a Vercel project?
|
||||
cat .vercel/project.json 2>/dev/null || cat .vercel/repo.json 2>/dev/null
|
||||
```
|
||||
|
||||
#### Link the project
|
||||
|
||||
**With git remote (preferred):**
|
||||
|
||||
```bash
|
||||
vercel link --repo --scope <team-slug> -y
|
||||
```
|
||||
|
||||
Reads the git remote and connects to the matching Vercel project. Creates `.vercel/repo.json`. More reliable than plain `vercel link`, which matches by directory name.
|
||||
|
||||
**Without git remote:**
|
||||
|
||||
```bash
|
||||
vercel link --scope <team-slug> -y
|
||||
```
|
||||
|
||||
Creates `.vercel/project.json`.
|
||||
|
||||
**Link to a specific project by name:**
|
||||
|
||||
```bash
|
||||
vercel link --project <project-name> --scope <team-slug> -y
|
||||
```
|
||||
|
||||
If the project is already linked, check `orgId` in `.vercel/project.json` or `.vercel/repo.json` to verify it matches the intended team.
|
||||
|
||||
#### Deploy after linking
|
||||
|
||||
**A) Git Push Deploy — has git remote (preferred)**
|
||||
|
||||
Git pushes trigger automatic Vercel deployments.
|
||||
|
||||
1. **Ask the user before pushing.** Never push without explicit approval.
|
||||
2. Commit and push:
|
||||
```bash
|
||||
git add .
|
||||
git commit -m "deploy: <description of changes>"
|
||||
git push
|
||||
```
|
||||
3. Vercel builds automatically. Non-production branches get preview deployments.
|
||||
4. Retrieve the deployment URL:
|
||||
```bash
|
||||
sleep 5
|
||||
vercel ls --format json --scope <team-slug>
|
||||
```
|
||||
Find the latest entry in the `deployments` array.
|
||||
|
||||
**B) CLI Deploy — no git remote**
|
||||
|
||||
```bash
|
||||
vercel deploy --scope <team-slug> -y --no-wait
|
||||
```
|
||||
|
||||
Check status:
|
||||
|
||||
```bash
|
||||
vercel inspect <deployment-url>
|
||||
```
|
||||
|
||||
### Deploying from a Remote Repository (code not cloned locally)
|
||||
|
||||
1. Clone the repository:
|
||||
```bash
|
||||
git clone <repo-url>
|
||||
cd <repo-name>
|
||||
```
|
||||
2. Link to Vercel:
|
||||
```bash
|
||||
vercel link --repo --scope <team-slug> -y
|
||||
```
|
||||
3. Deploy via git push (if you have push access) or CLI deploy.
|
||||
|
||||
### About `.vercel/` Directory
|
||||
|
||||
A linked project has either:
|
||||
- `.vercel/project.json` — from `vercel link`. Contains `projectId` and `orgId`.
|
||||
- `.vercel/repo.json` — from `vercel link --repo`. Contains `orgId`, `remoteName`, and a `projects` map.
|
||||
|
||||
Not needed when `VERCEL_ORG_ID` + `VERCEL_PROJECT_ID` are both set in the environment.
|
||||
|
||||
**Do NOT** run `vercel project inspect` or `vercel link` in an unlinked directory to detect state — they will interactively prompt or silently link as a side-effect. `vercel ls` is safe (in an unlinked directory it defaults to showing all deployments for the scope). `vercel whoami` is safe anywhere.
|
||||
|
||||
## Managing Environment Variables
|
||||
|
||||
```bash
|
||||
# Set for all environments
|
||||
echo "value" | vercel env add VAR_NAME --scope <team-slug>
|
||||
|
||||
# Set for a specific environment (production, preview, development)
|
||||
echo "value" | vercel env add VAR_NAME production --scope <team-slug>
|
||||
|
||||
# List environment variables
|
||||
vercel env ls --scope <team-slug>
|
||||
|
||||
# Pull env vars to local .env.local file
|
||||
vercel env pull --scope <team-slug>
|
||||
|
||||
# Remove a variable
|
||||
vercel env rm VAR_NAME --scope <team-slug> -y
|
||||
```
|
||||
|
||||
## Inspecting Deployments
|
||||
|
||||
```bash
|
||||
# List recent deployments
|
||||
vercel ls --format json --scope <team-slug>
|
||||
|
||||
# Inspect a specific deployment
|
||||
vercel inspect <deployment-url>
|
||||
|
||||
# View build logs (requires Vercel CLI v35+)
|
||||
vercel inspect <deployment-url> --logs
|
||||
|
||||
# View runtime request logs (follows live by default; add --no-follow for a one-shot snapshot)
|
||||
vercel logs <deployment-url>
|
||||
```
|
||||
|
||||
## Managing Domains
|
||||
|
||||
```bash
|
||||
# List domains
|
||||
vercel domains ls --scope <team-slug>
|
||||
|
||||
# Add a domain to the project — linked or env-linked directory (1 arg)
|
||||
vercel domains add <domain> --scope <team-slug>
|
||||
|
||||
# Add a domain — unlinked directory (requires <project> positional)
|
||||
vercel domains add <domain> <project> --scope <team-slug>
|
||||
```
|
||||
|
||||
## Stripe Projects Plan Changes
|
||||
|
||||
If this project is managed by Stripe Projects. **Ask the user before running any paid or destructive plan change** — upgrades bill a real card, downgrades remove seats.
|
||||
|
||||
First run `stripe projects status --json` to confirm the Vercel resource's local name. The examples below assume the default (`vercel-plan`); substitute the actual name if it was renamed at `stripe projects add` time.
|
||||
|
||||
- **Upgrade to Pro:** `stripe projects add vercel/pro` (or `stripe projects upgrade vercel-plan pro`)
|
||||
- **Downgrade to Hobby:** `stripe projects downgrade vercel-plan hobby`
|
||||
|
||||
### What Pro gives you
|
||||
|
||||
- $20/month platform fee, includes $20/month of usage credit.
|
||||
- Turbo build machines (30 vCPUs, 60 GB memory) by default for new projects — significantly faster builds than Hobby.
|
||||
- 1 deploying seat + unlimited free Viewer seats (read-only collaborators, preview comments).
|
||||
- Higher included allocations (1 TB Fast Data Transfer, 10M Edge Requests per month).
|
||||
- Paid add-ons available: SAML SSO, HIPAA BAA, Flags Explorer, Observability Plus, Speed Insights, Web Analytics Plus.
|
||||
|
||||
Full details: https://vercel.com/docs/plans/pro-plan
|
||||
|
||||
## Working Agreement
|
||||
|
||||
- **Never pass `VERCEL_TOKEN` as a `--token` flag.** Export it as an environment variable and let the CLI read it natively.
|
||||
- **Check the environment for tokens before asking the user.** Look in the current env and `.env` files first.
|
||||
- **Default to preview deployments.** Only deploy to production when explicitly asked.
|
||||
- **Ask before pushing to git.** Never push commits without the user's approval.
|
||||
- **Do not modify `.vercel/` files directly.** The CLI manages this directory. Reading them (e.g. to verify `orgId`) is fine.
|
||||
- **Do not curl/fetch deployed URLs to verify.** Just return the link to the user.
|
||||
- **Use `--format json`** when structured output will help with follow-up steps.
|
||||
- **Use `-y`** on commands that prompt for confirmation to avoid interactive blocking.
|
||||
|
||||
## Troubleshooting
|
||||
|
||||
### Token not found
|
||||
|
||||
Check the environment and any `.env` files present:
|
||||
|
||||
```bash
|
||||
printenv | grep -i vercel
|
||||
grep -i vercel .env 2>/dev/null
|
||||
```
|
||||
|
||||
### Authentication error
|
||||
|
||||
If the CLI fails with `Authentication required`:
|
||||
- The token may be expired or invalid.
|
||||
- Verify: `vercel whoami` (uses `VERCEL_TOKEN` from environment).
|
||||
- Ask the user for a fresh token.
|
||||
|
||||
### Wrong team
|
||||
|
||||
Verify the scope is correct:
|
||||
|
||||
```bash
|
||||
vercel whoami --scope <team-slug>
|
||||
```
|
||||
|
||||
### Build failure
|
||||
|
||||
Check the build logs:
|
||||
|
||||
```bash
|
||||
vercel inspect <deployment-url> --logs
|
||||
```
|
||||
|
||||
Common causes:
|
||||
- Missing dependencies — ensure `package.json` is complete and committed.
|
||||
- Missing environment variables — add with `vercel env add`.
|
||||
- Framework misconfiguration — check `vercel.json`. Vercel auto-detects frameworks (Next.js, Remix, Vite, etc.) from `package.json`; override with `vercel.json` if detection is wrong.
|
||||
|
||||
### CLI not installed
|
||||
|
||||
```bash
|
||||
npm install -g vercel
|
||||
```
|
||||
@@ -0,0 +1,946 @@
|
||||
# React Composition Patterns
|
||||
|
||||
**Version 1.0.0**
|
||||
Engineering
|
||||
January 2026
|
||||
|
||||
> **Note:**
|
||||
> This document is mainly for agents and LLMs to follow when maintaining,
|
||||
> generating, or refactoring React codebases using composition. Humans
|
||||
> may also find it useful, but guidance here is optimized for automation
|
||||
> and consistency by AI-assisted workflows.
|
||||
|
||||
---
|
||||
|
||||
## Abstract
|
||||
|
||||
Composition patterns for building flexible, maintainable React components. Avoid boolean prop proliferation by using compound components, lifting state, and composing internals. These patterns make codebases easier for both humans and AI agents to work with as they scale.
|
||||
|
||||
---
|
||||
|
||||
## Table of Contents
|
||||
|
||||
1. [Component Architecture](#1-component-architecture) — **HIGH**
|
||||
- 1.1 [Avoid Boolean Prop Proliferation](#11-avoid-boolean-prop-proliferation)
|
||||
- 1.2 [Use Compound Components](#12-use-compound-components)
|
||||
2. [State Management](#2-state-management) — **MEDIUM**
|
||||
- 2.1 [Decouple State Management from UI](#21-decouple-state-management-from-ui)
|
||||
- 2.2 [Define Generic Context Interfaces for Dependency Injection](#22-define-generic-context-interfaces-for-dependency-injection)
|
||||
- 2.3 [Lift State into Provider Components](#23-lift-state-into-provider-components)
|
||||
3. [Implementation Patterns](#3-implementation-patterns) — **MEDIUM**
|
||||
- 3.1 [Create Explicit Component Variants](#31-create-explicit-component-variants)
|
||||
- 3.2 [Prefer Composing Children Over Render Props](#32-prefer-composing-children-over-render-props)
|
||||
4. [React 19 APIs](#4-react-19-apis) — **MEDIUM**
|
||||
- 4.1 [React 19 API Changes](#41-react-19-api-changes)
|
||||
|
||||
---
|
||||
|
||||
## 1. Component Architecture
|
||||
|
||||
**Impact: HIGH**
|
||||
|
||||
Fundamental patterns for structuring components to avoid prop
|
||||
proliferation and enable flexible composition.
|
||||
|
||||
### 1.1 Avoid Boolean Prop Proliferation
|
||||
|
||||
**Impact: CRITICAL (prevents unmaintainable component variants)**
|
||||
|
||||
Don't add boolean props like `isThread`, `isEditing`, `isDMThread` to customize
|
||||
|
||||
component behavior. Each boolean doubles possible states and creates
|
||||
|
||||
unmaintainable conditional logic. Use composition instead.
|
||||
|
||||
**Incorrect: boolean props create exponential complexity**
|
||||
|
||||
```tsx
|
||||
function Composer({
|
||||
onSubmit,
|
||||
isThread,
|
||||
channelId,
|
||||
isDMThread,
|
||||
dmId,
|
||||
isEditing,
|
||||
isForwarding,
|
||||
}: Props) {
|
||||
return (
|
||||
<form>
|
||||
<Header />
|
||||
<Input />
|
||||
{isDMThread ? (
|
||||
<AlsoSendToDMField id={dmId} />
|
||||
) : isThread ? (
|
||||
<AlsoSendToChannelField id={channelId} />
|
||||
) : null}
|
||||
{isEditing ? (
|
||||
<EditActions />
|
||||
) : isForwarding ? (
|
||||
<ForwardActions />
|
||||
) : (
|
||||
<DefaultActions />
|
||||
)}
|
||||
<Footer onSubmit={onSubmit} />
|
||||
</form>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct: composition eliminates conditionals**
|
||||
|
||||
```tsx
|
||||
// Channel composer
|
||||
function ChannelComposer() {
|
||||
return (
|
||||
<Composer.Frame>
|
||||
<Composer.Header />
|
||||
<Composer.Input />
|
||||
<Composer.Footer>
|
||||
<Composer.Attachments />
|
||||
<Composer.Formatting />
|
||||
<Composer.Emojis />
|
||||
<Composer.Submit />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
)
|
||||
}
|
||||
|
||||
// Thread composer - adds "also send to channel" field
|
||||
function ThreadComposer({ channelId }: { channelId: string }) {
|
||||
return (
|
||||
<Composer.Frame>
|
||||
<Composer.Header />
|
||||
<Composer.Input />
|
||||
<AlsoSendToChannelField id={channelId} />
|
||||
<Composer.Footer>
|
||||
<Composer.Formatting />
|
||||
<Composer.Emojis />
|
||||
<Composer.Submit />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
)
|
||||
}
|
||||
|
||||
// Edit composer - different footer actions
|
||||
function EditComposer() {
|
||||
return (
|
||||
<Composer.Frame>
|
||||
<Composer.Input />
|
||||
<Composer.Footer>
|
||||
<Composer.Formatting />
|
||||
<Composer.Emojis />
|
||||
<Composer.CancelEdit />
|
||||
<Composer.SaveEdit />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
Each variant is explicit about what it renders. We can share internals without
|
||||
|
||||
sharing a single monolithic parent.
|
||||
|
||||
### 1.2 Use Compound Components
|
||||
|
||||
**Impact: HIGH (enables flexible composition without prop drilling)**
|
||||
|
||||
Structure complex components as compound components with a shared context. Each
|
||||
|
||||
subcomponent accesses shared state via context, not props. Consumers compose the
|
||||
|
||||
pieces they need.
|
||||
|
||||
**Incorrect: monolithic component with render props**
|
||||
|
||||
```tsx
|
||||
function Composer({
|
||||
renderHeader,
|
||||
renderFooter,
|
||||
renderActions,
|
||||
showAttachments,
|
||||
showFormatting,
|
||||
showEmojis,
|
||||
}: Props) {
|
||||
return (
|
||||
<form>
|
||||
{renderHeader?.()}
|
||||
<Input />
|
||||
{showAttachments && <Attachments />}
|
||||
{renderFooter ? (
|
||||
renderFooter()
|
||||
) : (
|
||||
<Footer>
|
||||
{showFormatting && <Formatting />}
|
||||
{showEmojis && <Emojis />}
|
||||
{renderActions?.()}
|
||||
</Footer>
|
||||
)}
|
||||
</form>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct: compound components with shared context**
|
||||
|
||||
```tsx
|
||||
const ComposerContext = createContext<ComposerContextValue | null>(null)
|
||||
|
||||
function ComposerProvider({ children, state, actions, meta }: ProviderProps) {
|
||||
return (
|
||||
<ComposerContext value={{ state, actions, meta }}>
|
||||
{children}
|
||||
</ComposerContext>
|
||||
)
|
||||
}
|
||||
|
||||
function ComposerFrame({ children }: { children: React.ReactNode }) {
|
||||
return <form>{children}</form>
|
||||
}
|
||||
|
||||
function ComposerInput() {
|
||||
const {
|
||||
state,
|
||||
actions: { update },
|
||||
meta: { inputRef },
|
||||
} = use(ComposerContext)
|
||||
return (
|
||||
<TextInput
|
||||
ref={inputRef}
|
||||
value={state.input}
|
||||
onChangeText={(text) => update((s) => ({ ...s, input: text }))}
|
||||
/>
|
||||
)
|
||||
}
|
||||
|
||||
function ComposerSubmit() {
|
||||
const {
|
||||
actions: { submit },
|
||||
} = use(ComposerContext)
|
||||
return <Button onPress={submit}>Send</Button>
|
||||
}
|
||||
|
||||
// Export as compound component
|
||||
const Composer = {
|
||||
Provider: ComposerProvider,
|
||||
Frame: ComposerFrame,
|
||||
Input: ComposerInput,
|
||||
Submit: ComposerSubmit,
|
||||
Header: ComposerHeader,
|
||||
Footer: ComposerFooter,
|
||||
Attachments: ComposerAttachments,
|
||||
Formatting: ComposerFormatting,
|
||||
Emojis: ComposerEmojis,
|
||||
}
|
||||
```
|
||||
|
||||
**Usage:**
|
||||
|
||||
```tsx
|
||||
<Composer.Provider state={state} actions={actions} meta={meta}>
|
||||
<Composer.Frame>
|
||||
<Composer.Header />
|
||||
<Composer.Input />
|
||||
<Composer.Footer>
|
||||
<Composer.Formatting />
|
||||
<Composer.Submit />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
</Composer.Provider>
|
||||
```
|
||||
|
||||
Consumers explicitly compose exactly what they need. No hidden conditionals. And the state, actions and meta are dependency-injected by a parent provider, allowing multiple usages of the same component structure.
|
||||
|
||||
---
|
||||
|
||||
## 2. State Management
|
||||
|
||||
**Impact: MEDIUM**
|
||||
|
||||
Patterns for lifting state and managing shared context across
|
||||
composed components.
|
||||
|
||||
### 2.1 Decouple State Management from UI
|
||||
|
||||
**Impact: MEDIUM (enables swapping state implementations without changing UI)**
|
||||
|
||||
The provider component should be the only place that knows how state is managed.
|
||||
|
||||
UI components consume the context interface—they don't know if state comes from
|
||||
|
||||
useState, Zustand, or a server sync.
|
||||
|
||||
**Incorrect: UI coupled to state implementation**
|
||||
|
||||
```tsx
|
||||
function ChannelComposer({ channelId }: { channelId: string }) {
|
||||
// UI component knows about global state implementation
|
||||
const state = useGlobalChannelState(channelId)
|
||||
const { submit, updateInput } = useChannelSync(channelId)
|
||||
|
||||
return (
|
||||
<Composer.Frame>
|
||||
<Composer.Input
|
||||
value={state.input}
|
||||
onChange={(text) => sync.updateInput(text)}
|
||||
/>
|
||||
<Composer.Submit onPress={() => sync.submit()} />
|
||||
</Composer.Frame>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct: state management isolated in provider**
|
||||
|
||||
```tsx
|
||||
// Provider handles all state management details
|
||||
function ChannelProvider({
|
||||
channelId,
|
||||
children,
|
||||
}: {
|
||||
channelId: string
|
||||
children: React.ReactNode
|
||||
}) {
|
||||
const { state, update, submit } = useGlobalChannel(channelId)
|
||||
const inputRef = useRef(null)
|
||||
|
||||
return (
|
||||
<Composer.Provider
|
||||
state={state}
|
||||
actions={{ update, submit }}
|
||||
meta={{ inputRef }}
|
||||
>
|
||||
{children}
|
||||
</Composer.Provider>
|
||||
)
|
||||
}
|
||||
|
||||
// UI component only knows about the context interface
|
||||
function ChannelComposer() {
|
||||
return (
|
||||
<Composer.Frame>
|
||||
<Composer.Header />
|
||||
<Composer.Input />
|
||||
<Composer.Footer>
|
||||
<Composer.Submit />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
)
|
||||
}
|
||||
|
||||
// Usage
|
||||
function Channel({ channelId }: { channelId: string }) {
|
||||
return (
|
||||
<ChannelProvider channelId={channelId}>
|
||||
<ChannelComposer />
|
||||
</ChannelProvider>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Different providers, same UI:**
|
||||
|
||||
```tsx
|
||||
// Local state for ephemeral forms
|
||||
function ForwardMessageProvider({ children }) {
|
||||
const [state, setState] = useState(initialState)
|
||||
const forwardMessage = useForwardMessage()
|
||||
|
||||
return (
|
||||
<Composer.Provider
|
||||
state={state}
|
||||
actions={{ update: setState, submit: forwardMessage }}
|
||||
>
|
||||
{children}
|
||||
</Composer.Provider>
|
||||
)
|
||||
}
|
||||
|
||||
// Global synced state for channels
|
||||
function ChannelProvider({ channelId, children }) {
|
||||
const { state, update, submit } = useGlobalChannel(channelId)
|
||||
|
||||
return (
|
||||
<Composer.Provider state={state} actions={{ update, submit }}>
|
||||
{children}
|
||||
</Composer.Provider>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
The same `Composer.Input` component works with both providers because it only
|
||||
|
||||
depends on the context interface, not the implementation.
|
||||
|
||||
### 2.2 Define Generic Context Interfaces for Dependency Injection
|
||||
|
||||
**Impact: HIGH (enables dependency-injectable state across use-cases)**
|
||||
|
||||
Define a **generic interface** for your component context with three parts:
|
||||
|
||||
`state`, `actions`, and `meta`. This interface is a contract that any provider
|
||||
|
||||
can implement—enabling the same UI components to work with completely different
|
||||
|
||||
state implementations.
|
||||
|
||||
**Core principle:** Lift state, compose internals, make state
|
||||
|
||||
dependency-injectable.
|
||||
|
||||
**Incorrect: UI coupled to specific state implementation**
|
||||
|
||||
```tsx
|
||||
function ComposerInput() {
|
||||
// Tightly coupled to a specific hook
|
||||
const { input, setInput } = useChannelComposerState()
|
||||
return <TextInput value={input} onChangeText={setInput} />
|
||||
}
|
||||
```
|
||||
|
||||
**Correct: generic interface enables dependency injection**
|
||||
|
||||
```tsx
|
||||
// Define a GENERIC interface that any provider can implement
|
||||
interface ComposerState {
|
||||
input: string
|
||||
attachments: Attachment[]
|
||||
isSubmitting: boolean
|
||||
}
|
||||
|
||||
interface ComposerActions {
|
||||
update: (updater: (state: ComposerState) => ComposerState) => void
|
||||
submit: () => void
|
||||
}
|
||||
|
||||
interface ComposerMeta {
|
||||
inputRef: React.RefObject<TextInput>
|
||||
}
|
||||
|
||||
interface ComposerContextValue {
|
||||
state: ComposerState
|
||||
actions: ComposerActions
|
||||
meta: ComposerMeta
|
||||
}
|
||||
|
||||
const ComposerContext = createContext<ComposerContextValue | null>(null)
|
||||
```
|
||||
|
||||
**UI components consume the interface, not the implementation:**
|
||||
|
||||
```tsx
|
||||
function ComposerInput() {
|
||||
const {
|
||||
state,
|
||||
actions: { update },
|
||||
meta,
|
||||
} = use(ComposerContext)
|
||||
|
||||
// This component works with ANY provider that implements the interface
|
||||
return (
|
||||
<TextInput
|
||||
ref={meta.inputRef}
|
||||
value={state.input}
|
||||
onChangeText={(text) => update((s) => ({ ...s, input: text }))}
|
||||
/>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Different providers implement the same interface:**
|
||||
|
||||
```tsx
|
||||
// Provider A: Local state for ephemeral forms
|
||||
function ForwardMessageProvider({ children }: { children: React.ReactNode }) {
|
||||
const [state, setState] = useState(initialState)
|
||||
const inputRef = useRef(null)
|
||||
const submit = useForwardMessage()
|
||||
|
||||
return (
|
||||
<ComposerContext
|
||||
value={{
|
||||
state,
|
||||
actions: { update: setState, submit },
|
||||
meta: { inputRef },
|
||||
}}
|
||||
>
|
||||
{children}
|
||||
</ComposerContext>
|
||||
)
|
||||
}
|
||||
|
||||
// Provider B: Global synced state for channels
|
||||
function ChannelProvider({ channelId, children }: Props) {
|
||||
const { state, update, submit } = useGlobalChannel(channelId)
|
||||
const inputRef = useRef(null)
|
||||
|
||||
return (
|
||||
<ComposerContext
|
||||
value={{
|
||||
state,
|
||||
actions: { update, submit },
|
||||
meta: { inputRef },
|
||||
}}
|
||||
>
|
||||
{children}
|
||||
</ComposerContext>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**The same composed UI works with both:**
|
||||
|
||||
```tsx
|
||||
// Works with ForwardMessageProvider (local state)
|
||||
<ForwardMessageProvider>
|
||||
<Composer.Frame>
|
||||
<Composer.Input />
|
||||
<Composer.Submit />
|
||||
</Composer.Frame>
|
||||
</ForwardMessageProvider>
|
||||
|
||||
// Works with ChannelProvider (global synced state)
|
||||
<ChannelProvider channelId="abc">
|
||||
<Composer.Frame>
|
||||
<Composer.Input />
|
||||
<Composer.Submit />
|
||||
</Composer.Frame>
|
||||
</ChannelProvider>
|
||||
```
|
||||
|
||||
**Custom UI outside the component can access state and actions:**
|
||||
|
||||
```tsx
|
||||
function ForwardMessageDialog() {
|
||||
return (
|
||||
<ForwardMessageProvider>
|
||||
<Dialog>
|
||||
{/* The composer UI */}
|
||||
<Composer.Frame>
|
||||
<Composer.Input placeholder="Add a message, if you'd like." />
|
||||
<Composer.Footer>
|
||||
<Composer.Formatting />
|
||||
<Composer.Emojis />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
|
||||
{/* Custom UI OUTSIDE the composer, but INSIDE the provider */}
|
||||
<MessagePreview />
|
||||
|
||||
{/* Actions at the bottom of the dialog */}
|
||||
<DialogActions>
|
||||
<CancelButton />
|
||||
<ForwardButton />
|
||||
</DialogActions>
|
||||
</Dialog>
|
||||
</ForwardMessageProvider>
|
||||
)
|
||||
}
|
||||
|
||||
// This button lives OUTSIDE Composer.Frame but can still submit based on its context!
|
||||
function ForwardButton() {
|
||||
const {
|
||||
actions: { submit },
|
||||
} = use(ComposerContext)
|
||||
return <Button onPress={submit}>Forward</Button>
|
||||
}
|
||||
|
||||
// This preview lives OUTSIDE Composer.Frame but can read composer's state!
|
||||
function MessagePreview() {
|
||||
const { state } = use(ComposerContext)
|
||||
return <Preview message={state.input} attachments={state.attachments} />
|
||||
}
|
||||
```
|
||||
|
||||
The provider boundary is what matters—not the visual nesting. Components that
|
||||
|
||||
need shared state don't have to be inside the `Composer.Frame`. They just need
|
||||
|
||||
to be within the provider.
|
||||
|
||||
The `ForwardButton` and `MessagePreview` are not visually inside the composer
|
||||
|
||||
box, but they can still access its state and actions. This is the power of
|
||||
|
||||
lifting state into providers.
|
||||
|
||||
The UI is reusable bits you compose together. The state is dependency-injected
|
||||
|
||||
by the provider. Swap the provider, keep the UI.
|
||||
|
||||
### 2.3 Lift State into Provider Components
|
||||
|
||||
**Impact: HIGH (enables state sharing outside component boundaries)**
|
||||
|
||||
Move state management into dedicated provider components. This allows sibling
|
||||
|
||||
components outside the main UI to access and modify state without prop drilling
|
||||
|
||||
or awkward refs.
|
||||
|
||||
**Incorrect: state trapped inside component**
|
||||
|
||||
```tsx
|
||||
function ForwardMessageComposer() {
|
||||
const [state, setState] = useState(initialState)
|
||||
const forwardMessage = useForwardMessage()
|
||||
|
||||
return (
|
||||
<Composer.Frame>
|
||||
<Composer.Input />
|
||||
<Composer.Footer />
|
||||
</Composer.Frame>
|
||||
)
|
||||
}
|
||||
|
||||
// Problem: How does this button access composer state?
|
||||
function ForwardMessageDialog() {
|
||||
return (
|
||||
<Dialog>
|
||||
<ForwardMessageComposer />
|
||||
<MessagePreview /> {/* Needs composer state */}
|
||||
<DialogActions>
|
||||
<CancelButton />
|
||||
<ForwardButton /> {/* Needs to call submit */}
|
||||
</DialogActions>
|
||||
</Dialog>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Incorrect: useEffect to sync state up**
|
||||
|
||||
```tsx
|
||||
function ForwardMessageDialog() {
|
||||
const [input, setInput] = useState('')
|
||||
return (
|
||||
<Dialog>
|
||||
<ForwardMessageComposer onInputChange={setInput} />
|
||||
<MessagePreview input={input} />
|
||||
</Dialog>
|
||||
)
|
||||
}
|
||||
|
||||
function ForwardMessageComposer({ onInputChange }) {
|
||||
const [state, setState] = useState(initialState)
|
||||
useEffect(() => {
|
||||
onInputChange(state.input) // Sync on every change 😬
|
||||
}, [state.input])
|
||||
}
|
||||
```
|
||||
|
||||
**Incorrect: reading state from ref on submit**
|
||||
|
||||
```tsx
|
||||
function ForwardMessageDialog() {
|
||||
const stateRef = useRef(null)
|
||||
return (
|
||||
<Dialog>
|
||||
<ForwardMessageComposer stateRef={stateRef} />
|
||||
<ForwardButton onPress={() => submit(stateRef.current)} />
|
||||
</Dialog>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct: state lifted to provider**
|
||||
|
||||
```tsx
|
||||
function ForwardMessageProvider({ children }: { children: React.ReactNode }) {
|
||||
const [state, setState] = useState(initialState)
|
||||
const forwardMessage = useForwardMessage()
|
||||
const inputRef = useRef(null)
|
||||
|
||||
return (
|
||||
<Composer.Provider
|
||||
state={state}
|
||||
actions={{ update: setState, submit: forwardMessage }}
|
||||
meta={{ inputRef }}
|
||||
>
|
||||
{children}
|
||||
</Composer.Provider>
|
||||
)
|
||||
}
|
||||
|
||||
function ForwardMessageDialog() {
|
||||
return (
|
||||
<ForwardMessageProvider>
|
||||
<Dialog>
|
||||
<ForwardMessageComposer />
|
||||
<MessagePreview /> {/* Custom components can access state and actions */}
|
||||
<DialogActions>
|
||||
<CancelButton />
|
||||
<ForwardButton /> {/* Custom components can access state and actions */}
|
||||
</DialogActions>
|
||||
</Dialog>
|
||||
</ForwardMessageProvider>
|
||||
)
|
||||
}
|
||||
|
||||
function ForwardButton() {
|
||||
const { actions } = use(Composer.Context)
|
||||
return <Button onPress={actions.submit}>Forward</Button>
|
||||
}
|
||||
```
|
||||
|
||||
The ForwardButton lives outside the Composer.Frame but still has access to the
|
||||
|
||||
submit action because it's within the provider. Even though it's a one-off
|
||||
|
||||
component, it can still access the composer's state and actions from outside the
|
||||
|
||||
UI itself.
|
||||
|
||||
**Key insight:** Components that need shared state don't have to be visually
|
||||
|
||||
nested inside each other—they just need to be within the same provider.
|
||||
|
||||
---
|
||||
|
||||
## 3. Implementation Patterns
|
||||
|
||||
**Impact: MEDIUM**
|
||||
|
||||
Specific techniques for implementing compound components and
|
||||
context providers.
|
||||
|
||||
### 3.1 Create Explicit Component Variants
|
||||
|
||||
**Impact: MEDIUM (self-documenting code, no hidden conditionals)**
|
||||
|
||||
Instead of one component with many boolean props, create explicit variant
|
||||
|
||||
components. Each variant composes the pieces it needs. The code documents
|
||||
|
||||
itself.
|
||||
|
||||
**Incorrect: one component, many modes**
|
||||
|
||||
```tsx
|
||||
// What does this component actually render?
|
||||
<Composer
|
||||
isThread
|
||||
isEditing={false}
|
||||
channelId='abc'
|
||||
showAttachments
|
||||
showFormatting={false}
|
||||
/>
|
||||
```
|
||||
|
||||
**Correct: explicit variants**
|
||||
|
||||
```tsx
|
||||
// Immediately clear what this renders
|
||||
<ThreadComposer channelId="abc" />
|
||||
|
||||
// Or
|
||||
<EditMessageComposer messageId="xyz" />
|
||||
|
||||
// Or
|
||||
<ForwardMessageComposer messageId="123" />
|
||||
```
|
||||
|
||||
Each implementation is unique, explicit and self-contained. Yet they can each
|
||||
|
||||
use shared parts.
|
||||
|
||||
**Implementation:**
|
||||
|
||||
```tsx
|
||||
function ThreadComposer({ channelId }: { channelId: string }) {
|
||||
return (
|
||||
<ThreadProvider channelId={channelId}>
|
||||
<Composer.Frame>
|
||||
<Composer.Input />
|
||||
<AlsoSendToChannelField channelId={channelId} />
|
||||
<Composer.Footer>
|
||||
<Composer.Formatting />
|
||||
<Composer.Emojis />
|
||||
<Composer.Submit />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
</ThreadProvider>
|
||||
)
|
||||
}
|
||||
|
||||
function EditMessageComposer({ messageId }: { messageId: string }) {
|
||||
return (
|
||||
<EditMessageProvider messageId={messageId}>
|
||||
<Composer.Frame>
|
||||
<Composer.Input />
|
||||
<Composer.Footer>
|
||||
<Composer.Formatting />
|
||||
<Composer.Emojis />
|
||||
<Composer.CancelEdit />
|
||||
<Composer.SaveEdit />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
</EditMessageProvider>
|
||||
)
|
||||
}
|
||||
|
||||
function ForwardMessageComposer({ messageId }: { messageId: string }) {
|
||||
return (
|
||||
<ForwardMessageProvider messageId={messageId}>
|
||||
<Composer.Frame>
|
||||
<Composer.Input placeholder="Add a message, if you'd like." />
|
||||
<Composer.Footer>
|
||||
<Composer.Formatting />
|
||||
<Composer.Emojis />
|
||||
<Composer.Mentions />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
</ForwardMessageProvider>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
Each variant is explicit about:
|
||||
|
||||
- What provider/state it uses
|
||||
|
||||
- What UI elements it includes
|
||||
|
||||
- What actions are available
|
||||
|
||||
No boolean prop combinations to reason about. No impossible states.
|
||||
|
||||
### 3.2 Prefer Composing Children Over Render Props
|
||||
|
||||
**Impact: MEDIUM (cleaner composition, better readability)**
|
||||
|
||||
Use `children` for composition instead of `renderX` props. Children are more
|
||||
|
||||
readable, compose naturally, and don't require understanding callback
|
||||
|
||||
signatures.
|
||||
|
||||
**Incorrect: render props**
|
||||
|
||||
```tsx
|
||||
function Composer({
|
||||
renderHeader,
|
||||
renderFooter,
|
||||
renderActions,
|
||||
}: {
|
||||
renderHeader?: () => React.ReactNode
|
||||
renderFooter?: () => React.ReactNode
|
||||
renderActions?: () => React.ReactNode
|
||||
}) {
|
||||
return (
|
||||
<form>
|
||||
{renderHeader?.()}
|
||||
<Input />
|
||||
{renderFooter ? renderFooter() : <DefaultFooter />}
|
||||
{renderActions?.()}
|
||||
</form>
|
||||
)
|
||||
}
|
||||
|
||||
// Usage is awkward and inflexible
|
||||
return (
|
||||
<Composer
|
||||
renderHeader={() => <CustomHeader />}
|
||||
renderFooter={() => (
|
||||
<>
|
||||
<Formatting />
|
||||
<Emojis />
|
||||
</>
|
||||
)}
|
||||
renderActions={() => <SubmitButton />}
|
||||
/>
|
||||
)
|
||||
```
|
||||
|
||||
**Correct: compound components with children**
|
||||
|
||||
```tsx
|
||||
function ComposerFrame({ children }: { children: React.ReactNode }) {
|
||||
return <form>{children}</form>
|
||||
}
|
||||
|
||||
function ComposerFooter({ children }: { children: React.ReactNode }) {
|
||||
return <footer className='flex'>{children}</footer>
|
||||
}
|
||||
|
||||
// Usage is flexible
|
||||
return (
|
||||
<Composer.Frame>
|
||||
<CustomHeader />
|
||||
<Composer.Input />
|
||||
<Composer.Footer>
|
||||
<Composer.Formatting />
|
||||
<Composer.Emojis />
|
||||
<SubmitButton />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
)
|
||||
```
|
||||
|
||||
**When render props are appropriate:**
|
||||
|
||||
```tsx
|
||||
// Render props work well when you need to pass data back
|
||||
<List
|
||||
data={items}
|
||||
renderItem={({ item, index }) => <Item item={item} index={index} />}
|
||||
/>
|
||||
```
|
||||
|
||||
Use render props when the parent needs to provide data or state to the child.
|
||||
|
||||
Use children when composing static structure.
|
||||
|
||||
---
|
||||
|
||||
## 4. React 19 APIs
|
||||
|
||||
**Impact: MEDIUM**
|
||||
|
||||
React 19+ only. Don't use `forwardRef`; use `use()` instead of `useContext()`.
|
||||
|
||||
### 4.1 React 19 API Changes
|
||||
|
||||
**Impact: MEDIUM (cleaner component definitions and context usage)**
|
||||
|
||||
> **⚠️ React 19+ only.** Skip this if you're on React 18 or earlier.
|
||||
|
||||
In React 19, `ref` is now a regular prop (no `forwardRef` wrapper needed), and `use()` replaces `useContext()`.
|
||||
|
||||
**Incorrect: forwardRef in React 19**
|
||||
|
||||
```tsx
|
||||
const ComposerInput = forwardRef<TextInput, Props>((props, ref) => {
|
||||
return <TextInput ref={ref} {...props} />
|
||||
})
|
||||
```
|
||||
|
||||
**Correct: ref as a regular prop**
|
||||
|
||||
```tsx
|
||||
function ComposerInput({ ref, ...props }: Props & { ref?: React.Ref<TextInput> }) {
|
||||
return <TextInput ref={ref} {...props} />
|
||||
}
|
||||
```
|
||||
|
||||
**Incorrect: useContext in React 19**
|
||||
|
||||
```tsx
|
||||
const value = useContext(MyContext)
|
||||
```
|
||||
|
||||
**Correct: use instead of useContext**
|
||||
|
||||
```tsx
|
||||
const value = use(MyContext)
|
||||
```
|
||||
|
||||
`use()` can also be called conditionally, unlike `useContext()`.
|
||||
|
||||
---
|
||||
|
||||
## References
|
||||
|
||||
1. [https://react.dev](https://react.dev)
|
||||
2. [https://react.dev/learn/passing-data-deeply-with-context](https://react.dev/learn/passing-data-deeply-with-context)
|
||||
3. [https://react.dev/reference/react/use](https://react.dev/reference/react/use)
|
||||
@@ -0,0 +1,60 @@
|
||||
# React Composition Patterns
|
||||
|
||||
A structured repository for React composition patterns that scale. These
|
||||
patterns help avoid boolean prop proliferation by using compound components,
|
||||
lifting state, and composing internals.
|
||||
|
||||
## Structure
|
||||
|
||||
- `rules/` - Individual rule files (one per rule)
|
||||
- `_sections.md` - Section metadata (titles, impacts, descriptions)
|
||||
- `_template.md` - Template for creating new rules
|
||||
- `area-description.md` - Individual rule files
|
||||
- `metadata.json` - Document metadata (version, organization, abstract)
|
||||
- **`AGENTS.md`** - Compiled output (generated)
|
||||
|
||||
## Rules
|
||||
|
||||
### Component Architecture (CRITICAL)
|
||||
|
||||
- `architecture-avoid-boolean-props.md` - Don't add boolean props to customize
|
||||
behavior
|
||||
- `architecture-compound-components.md` - Structure as compound components with
|
||||
shared context
|
||||
|
||||
### State Management (HIGH)
|
||||
|
||||
- `state-lift-state.md` - Lift state into provider components
|
||||
- `state-context-interface.md` - Define clear context interfaces
|
||||
(state/actions/meta)
|
||||
- `state-decouple-implementation.md` - Decouple state management from UI
|
||||
|
||||
### Implementation Patterns (MEDIUM)
|
||||
|
||||
- `patterns-children-over-render-props.md` - Prefer children over renderX props
|
||||
- `patterns-explicit-variants.md` - Create explicit component variants
|
||||
|
||||
## Core Principles
|
||||
|
||||
1. **Composition over configuration** — Instead of adding props, let consumers
|
||||
compose
|
||||
2. **Lift your state** — State in providers, not trapped in components
|
||||
3. **Compose your internals** — Subcomponents access context, not props
|
||||
4. **Explicit variants** — Create ThreadComposer, EditComposer, not Composer
|
||||
with isThread
|
||||
|
||||
## Creating a New Rule
|
||||
|
||||
1. Copy `rules/_template.md` to `rules/area-description.md`
|
||||
2. Choose the appropriate area prefix:
|
||||
- `architecture-` for Component Architecture
|
||||
- `state-` for State Management
|
||||
- `patterns-` for Implementation Patterns
|
||||
3. Fill in the frontmatter and content
|
||||
4. Ensure you have clear examples with explanations
|
||||
|
||||
## Impact Levels
|
||||
|
||||
- `CRITICAL` - Foundational patterns, prevents unmaintainable code
|
||||
- `HIGH` - Significant maintainability improvements
|
||||
- `MEDIUM` - Good practices for cleaner code
|
||||
@@ -0,0 +1,89 @@
|
||||
---
|
||||
name: vercel-composition-patterns
|
||||
description:
|
||||
React composition patterns that scale. Use when refactoring components with
|
||||
boolean prop proliferation, building flexible component libraries, or
|
||||
designing reusable APIs. Triggers on tasks involving compound components,
|
||||
render props, context providers, or component architecture. Includes React 19
|
||||
API changes.
|
||||
license: MIT
|
||||
metadata:
|
||||
author: vercel
|
||||
version: '1.0.0'
|
||||
---
|
||||
|
||||
# React Composition Patterns
|
||||
|
||||
Composition patterns for building flexible, maintainable React components. Avoid
|
||||
boolean prop proliferation by using compound components, lifting state, and
|
||||
composing internals. These patterns make codebases easier for both humans and AI
|
||||
agents to work with as they scale.
|
||||
|
||||
## When to Apply
|
||||
|
||||
Reference these guidelines when:
|
||||
|
||||
- Refactoring components with many boolean props
|
||||
- Building reusable component libraries
|
||||
- Designing flexible component APIs
|
||||
- Reviewing component architecture
|
||||
- Working with compound components or context providers
|
||||
|
||||
## Rule Categories by Priority
|
||||
|
||||
| Priority | Category | Impact | Prefix |
|
||||
| -------- | ----------------------- | ------ | --------------- |
|
||||
| 1 | Component Architecture | HIGH | `architecture-` |
|
||||
| 2 | State Management | MEDIUM | `state-` |
|
||||
| 3 | Implementation Patterns | MEDIUM | `patterns-` |
|
||||
| 4 | React 19 APIs | MEDIUM | `react19-` |
|
||||
|
||||
## Quick Reference
|
||||
|
||||
### 1. Component Architecture (HIGH)
|
||||
|
||||
- `architecture-avoid-boolean-props` - Don't add boolean props to customize
|
||||
behavior; use composition
|
||||
- `architecture-compound-components` - Structure complex components with shared
|
||||
context
|
||||
|
||||
### 2. State Management (MEDIUM)
|
||||
|
||||
- `state-decouple-implementation` - Provider is the only place that knows how
|
||||
state is managed
|
||||
- `state-context-interface` - Define generic interface with state, actions, meta
|
||||
for dependency injection
|
||||
- `state-lift-state` - Move state into provider components for sibling access
|
||||
|
||||
### 3. Implementation Patterns (MEDIUM)
|
||||
|
||||
- `patterns-explicit-variants` - Create explicit variant components instead of
|
||||
boolean modes
|
||||
- `patterns-children-over-render-props` - Use children for composition instead
|
||||
of renderX props
|
||||
|
||||
### 4. React 19 APIs (MEDIUM)
|
||||
|
||||
> **⚠️ React 19+ only.** Skip this section if using React 18 or earlier.
|
||||
|
||||
- `react19-no-forwardref` - Don't use `forwardRef`; use `use()` instead of `useContext()`
|
||||
|
||||
## How to Use
|
||||
|
||||
Read individual rule files for detailed explanations and code examples:
|
||||
|
||||
```
|
||||
rules/architecture-avoid-boolean-props.md
|
||||
rules/state-context-interface.md
|
||||
```
|
||||
|
||||
Each rule file contains:
|
||||
|
||||
- Brief explanation of why it matters
|
||||
- Incorrect code example with explanation
|
||||
- Correct code example with explanation
|
||||
- Additional context and references
|
||||
|
||||
## Full Compiled Document
|
||||
|
||||
For the complete guide with all rules expanded: `AGENTS.md`
|
||||
@@ -0,0 +1,11 @@
|
||||
{
|
||||
"version": "1.0.0",
|
||||
"organization": "Engineering",
|
||||
"date": "January 2026",
|
||||
"abstract": "Composition patterns for building flexible, maintainable React components. Avoid boolean prop proliferation by using compound components, lifting state, and composing internals. These patterns make codebases easier for both humans and AI agents to work with as they scale.",
|
||||
"references": [
|
||||
"https://react.dev",
|
||||
"https://react.dev/learn/passing-data-deeply-with-context",
|
||||
"https://react.dev/reference/react/use"
|
||||
]
|
||||
}
|
||||
@@ -0,0 +1,29 @@
|
||||
# Sections
|
||||
|
||||
This file defines all sections, their ordering, impact levels, and descriptions.
|
||||
The section ID (in parentheses) is the filename prefix used to group rules.
|
||||
|
||||
---
|
||||
|
||||
## 1. Component Architecture (architecture)
|
||||
|
||||
**Impact:** HIGH
|
||||
**Description:** Fundamental patterns for structuring components to avoid prop
|
||||
proliferation and enable flexible composition.
|
||||
|
||||
## 2. State Management (state)
|
||||
|
||||
**Impact:** MEDIUM
|
||||
**Description:** Patterns for lifting state and managing shared context across
|
||||
composed components.
|
||||
|
||||
## 3. Implementation Patterns (patterns)
|
||||
|
||||
**Impact:** MEDIUM
|
||||
**Description:** Specific techniques for implementing compound components and
|
||||
context providers.
|
||||
|
||||
## 4. React 19 APIs (react19)
|
||||
|
||||
**Impact:** MEDIUM
|
||||
**Description:** React 19+ only. Don't use `forwardRef`; use `use()` instead of `useContext()`.
|
||||
@@ -0,0 +1,24 @@
|
||||
---
|
||||
title: Rule Title Here
|
||||
impact: MEDIUM
|
||||
impactDescription: brief description of impact
|
||||
tags: composition, components
|
||||
---
|
||||
|
||||
## Rule Title Here
|
||||
|
||||
Brief explanation of the rule and why it matters.
|
||||
|
||||
**Incorrect:**
|
||||
|
||||
```tsx
|
||||
// Bad code example
|
||||
```
|
||||
|
||||
**Correct:**
|
||||
|
||||
```tsx
|
||||
// Good code example
|
||||
```
|
||||
|
||||
Reference: [Link](https://example.com)
|
||||
@@ -0,0 +1,100 @@
|
||||
---
|
||||
title: Avoid Boolean Prop Proliferation
|
||||
impact: CRITICAL
|
||||
impactDescription: prevents unmaintainable component variants
|
||||
tags: composition, props, architecture
|
||||
---
|
||||
|
||||
## Avoid Boolean Prop Proliferation
|
||||
|
||||
Don't add boolean props like `isThread`, `isEditing`, `isDMThread` to customize
|
||||
component behavior. Each boolean doubles possible states and creates
|
||||
unmaintainable conditional logic. Use composition instead.
|
||||
|
||||
**Incorrect (boolean props create exponential complexity):**
|
||||
|
||||
```tsx
|
||||
function Composer({
|
||||
onSubmit,
|
||||
isThread,
|
||||
channelId,
|
||||
isDMThread,
|
||||
dmId,
|
||||
isEditing,
|
||||
isForwarding,
|
||||
}: Props) {
|
||||
return (
|
||||
<form>
|
||||
<Header />
|
||||
<Input />
|
||||
{isDMThread ? (
|
||||
<AlsoSendToDMField id={dmId} />
|
||||
) : isThread ? (
|
||||
<AlsoSendToChannelField id={channelId} />
|
||||
) : null}
|
||||
{isEditing ? (
|
||||
<EditActions />
|
||||
) : isForwarding ? (
|
||||
<ForwardActions />
|
||||
) : (
|
||||
<DefaultActions />
|
||||
)}
|
||||
<Footer onSubmit={onSubmit} />
|
||||
</form>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (composition eliminates conditionals):**
|
||||
|
||||
```tsx
|
||||
// Channel composer
|
||||
function ChannelComposer() {
|
||||
return (
|
||||
<Composer.Frame>
|
||||
<Composer.Header />
|
||||
<Composer.Input />
|
||||
<Composer.Footer>
|
||||
<Composer.Attachments />
|
||||
<Composer.Formatting />
|
||||
<Composer.Emojis />
|
||||
<Composer.Submit />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
)
|
||||
}
|
||||
|
||||
// Thread composer - adds "also send to channel" field
|
||||
function ThreadComposer({ channelId }: { channelId: string }) {
|
||||
return (
|
||||
<Composer.Frame>
|
||||
<Composer.Header />
|
||||
<Composer.Input />
|
||||
<AlsoSendToChannelField id={channelId} />
|
||||
<Composer.Footer>
|
||||
<Composer.Formatting />
|
||||
<Composer.Emojis />
|
||||
<Composer.Submit />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
)
|
||||
}
|
||||
|
||||
// Edit composer - different footer actions
|
||||
function EditComposer() {
|
||||
return (
|
||||
<Composer.Frame>
|
||||
<Composer.Input />
|
||||
<Composer.Footer>
|
||||
<Composer.Formatting />
|
||||
<Composer.Emojis />
|
||||
<Composer.CancelEdit />
|
||||
<Composer.SaveEdit />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
Each variant is explicit about what it renders. We can share internals without
|
||||
sharing a single monolithic parent.
|
||||
@@ -0,0 +1,112 @@
|
||||
---
|
||||
title: Use Compound Components
|
||||
impact: HIGH
|
||||
impactDescription: enables flexible composition without prop drilling
|
||||
tags: composition, compound-components, architecture
|
||||
---
|
||||
|
||||
## Use Compound Components
|
||||
|
||||
Structure complex components as compound components with a shared context. Each
|
||||
subcomponent accesses shared state via context, not props. Consumers compose the
|
||||
pieces they need.
|
||||
|
||||
**Incorrect (monolithic component with render props):**
|
||||
|
||||
```tsx
|
||||
function Composer({
|
||||
renderHeader,
|
||||
renderFooter,
|
||||
renderActions,
|
||||
showAttachments,
|
||||
showFormatting,
|
||||
showEmojis,
|
||||
}: Props) {
|
||||
return (
|
||||
<form>
|
||||
{renderHeader?.()}
|
||||
<Input />
|
||||
{showAttachments && <Attachments />}
|
||||
{renderFooter ? (
|
||||
renderFooter()
|
||||
) : (
|
||||
<Footer>
|
||||
{showFormatting && <Formatting />}
|
||||
{showEmojis && <Emojis />}
|
||||
{renderActions?.()}
|
||||
</Footer>
|
||||
)}
|
||||
</form>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (compound components with shared context):**
|
||||
|
||||
```tsx
|
||||
const ComposerContext = createContext<ComposerContextValue | null>(null)
|
||||
|
||||
function ComposerProvider({ children, state, actions, meta }: ProviderProps) {
|
||||
return (
|
||||
<ComposerContext value={{ state, actions, meta }}>
|
||||
{children}
|
||||
</ComposerContext>
|
||||
)
|
||||
}
|
||||
|
||||
function ComposerFrame({ children }: { children: React.ReactNode }) {
|
||||
return <form>{children}</form>
|
||||
}
|
||||
|
||||
function ComposerInput() {
|
||||
const {
|
||||
state,
|
||||
actions: { update },
|
||||
meta: { inputRef },
|
||||
} = use(ComposerContext)
|
||||
return (
|
||||
<TextInput
|
||||
ref={inputRef}
|
||||
value={state.input}
|
||||
onChangeText={(text) => update((s) => ({ ...s, input: text }))}
|
||||
/>
|
||||
)
|
||||
}
|
||||
|
||||
function ComposerSubmit() {
|
||||
const {
|
||||
actions: { submit },
|
||||
} = use(ComposerContext)
|
||||
return <Button onPress={submit}>Send</Button>
|
||||
}
|
||||
|
||||
// Export as compound component
|
||||
const Composer = {
|
||||
Provider: ComposerProvider,
|
||||
Frame: ComposerFrame,
|
||||
Input: ComposerInput,
|
||||
Submit: ComposerSubmit,
|
||||
Header: ComposerHeader,
|
||||
Footer: ComposerFooter,
|
||||
Attachments: ComposerAttachments,
|
||||
Formatting: ComposerFormatting,
|
||||
Emojis: ComposerEmojis,
|
||||
}
|
||||
```
|
||||
|
||||
**Usage:**
|
||||
|
||||
```tsx
|
||||
<Composer.Provider state={state} actions={actions} meta={meta}>
|
||||
<Composer.Frame>
|
||||
<Composer.Header />
|
||||
<Composer.Input />
|
||||
<Composer.Footer>
|
||||
<Composer.Formatting />
|
||||
<Composer.Submit />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
</Composer.Provider>
|
||||
```
|
||||
|
||||
Consumers explicitly compose exactly what they need. No hidden conditionals. And the state, actions and meta are dependency-injected by a parent provider, allowing multiple usages of the same component structure.
|
||||
+87
@@ -0,0 +1,87 @@
|
||||
---
|
||||
title: Prefer Composing Children Over Render Props
|
||||
impact: MEDIUM
|
||||
impactDescription: cleaner composition, better readability
|
||||
tags: composition, children, render-props
|
||||
---
|
||||
|
||||
## Prefer Children Over Render Props
|
||||
|
||||
Use `children` for composition instead of `renderX` props. Children are more
|
||||
readable, compose naturally, and don't require understanding callback
|
||||
signatures.
|
||||
|
||||
**Incorrect (render props):**
|
||||
|
||||
```tsx
|
||||
function Composer({
|
||||
renderHeader,
|
||||
renderFooter,
|
||||
renderActions,
|
||||
}: {
|
||||
renderHeader?: () => React.ReactNode
|
||||
renderFooter?: () => React.ReactNode
|
||||
renderActions?: () => React.ReactNode
|
||||
}) {
|
||||
return (
|
||||
<form>
|
||||
{renderHeader?.()}
|
||||
<Input />
|
||||
{renderFooter ? renderFooter() : <DefaultFooter />}
|
||||
{renderActions?.()}
|
||||
</form>
|
||||
)
|
||||
}
|
||||
|
||||
// Usage is awkward and inflexible
|
||||
return (
|
||||
<Composer
|
||||
renderHeader={() => <CustomHeader />}
|
||||
renderFooter={() => (
|
||||
<>
|
||||
<Formatting />
|
||||
<Emojis />
|
||||
</>
|
||||
)}
|
||||
renderActions={() => <SubmitButton />}
|
||||
/>
|
||||
)
|
||||
```
|
||||
|
||||
**Correct (compound components with children):**
|
||||
|
||||
```tsx
|
||||
function ComposerFrame({ children }: { children: React.ReactNode }) {
|
||||
return <form>{children}</form>
|
||||
}
|
||||
|
||||
function ComposerFooter({ children }: { children: React.ReactNode }) {
|
||||
return <footer className='flex'>{children}</footer>
|
||||
}
|
||||
|
||||
// Usage is flexible
|
||||
return (
|
||||
<Composer.Frame>
|
||||
<CustomHeader />
|
||||
<Composer.Input />
|
||||
<Composer.Footer>
|
||||
<Composer.Formatting />
|
||||
<Composer.Emojis />
|
||||
<SubmitButton />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
)
|
||||
```
|
||||
|
||||
**When render props are appropriate:**
|
||||
|
||||
```tsx
|
||||
// Render props work well when you need to pass data back
|
||||
<List
|
||||
data={items}
|
||||
renderItem={({ item, index }) => <Item item={item} index={index} />}
|
||||
/>
|
||||
```
|
||||
|
||||
Use render props when the parent needs to provide data or state to the child.
|
||||
Use children when composing static structure.
|
||||
@@ -0,0 +1,100 @@
|
||||
---
|
||||
title: Create Explicit Component Variants
|
||||
impact: MEDIUM
|
||||
impactDescription: self-documenting code, no hidden conditionals
|
||||
tags: composition, variants, architecture
|
||||
---
|
||||
|
||||
## Create Explicit Component Variants
|
||||
|
||||
Instead of one component with many boolean props, create explicit variant
|
||||
components. Each variant composes the pieces it needs. The code documents
|
||||
itself.
|
||||
|
||||
**Incorrect (one component, many modes):**
|
||||
|
||||
```tsx
|
||||
// What does this component actually render?
|
||||
<Composer
|
||||
isThread
|
||||
isEditing={false}
|
||||
channelId='abc'
|
||||
showAttachments
|
||||
showFormatting={false}
|
||||
/>
|
||||
```
|
||||
|
||||
**Correct (explicit variants):**
|
||||
|
||||
```tsx
|
||||
// Immediately clear what this renders
|
||||
<ThreadComposer channelId="abc" />
|
||||
|
||||
// Or
|
||||
<EditMessageComposer messageId="xyz" />
|
||||
|
||||
// Or
|
||||
<ForwardMessageComposer messageId="123" />
|
||||
```
|
||||
|
||||
Each implementation is unique, explicit and self-contained. Yet they can each
|
||||
use shared parts.
|
||||
|
||||
**Implementation:**
|
||||
|
||||
```tsx
|
||||
function ThreadComposer({ channelId }: { channelId: string }) {
|
||||
return (
|
||||
<ThreadProvider channelId={channelId}>
|
||||
<Composer.Frame>
|
||||
<Composer.Input />
|
||||
<AlsoSendToChannelField channelId={channelId} />
|
||||
<Composer.Footer>
|
||||
<Composer.Formatting />
|
||||
<Composer.Emojis />
|
||||
<Composer.Submit />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
</ThreadProvider>
|
||||
)
|
||||
}
|
||||
|
||||
function EditMessageComposer({ messageId }: { messageId: string }) {
|
||||
return (
|
||||
<EditMessageProvider messageId={messageId}>
|
||||
<Composer.Frame>
|
||||
<Composer.Input />
|
||||
<Composer.Footer>
|
||||
<Composer.Formatting />
|
||||
<Composer.Emojis />
|
||||
<Composer.CancelEdit />
|
||||
<Composer.SaveEdit />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
</EditMessageProvider>
|
||||
)
|
||||
}
|
||||
|
||||
function ForwardMessageComposer({ messageId }: { messageId: string }) {
|
||||
return (
|
||||
<ForwardMessageProvider messageId={messageId}>
|
||||
<Composer.Frame>
|
||||
<Composer.Input placeholder="Add a message, if you'd like." />
|
||||
<Composer.Footer>
|
||||
<Composer.Formatting />
|
||||
<Composer.Emojis />
|
||||
<Composer.Mentions />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
</ForwardMessageProvider>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
Each variant is explicit about:
|
||||
|
||||
- What provider/state it uses
|
||||
- What UI elements it includes
|
||||
- What actions are available
|
||||
|
||||
No boolean prop combinations to reason about. No impossible states.
|
||||
@@ -0,0 +1,42 @@
|
||||
---
|
||||
title: React 19 API Changes
|
||||
impact: MEDIUM
|
||||
impactDescription: cleaner component definitions and context usage
|
||||
tags: react19, refs, context, hooks
|
||||
---
|
||||
|
||||
## React 19 API Changes
|
||||
|
||||
> **⚠️ React 19+ only.** Skip this if you're on React 18 or earlier.
|
||||
|
||||
In React 19, `ref` is now a regular prop (no `forwardRef` wrapper needed), and `use()` replaces `useContext()`.
|
||||
|
||||
**Incorrect (forwardRef in React 19):**
|
||||
|
||||
```tsx
|
||||
const ComposerInput = forwardRef<TextInput, Props>((props, ref) => {
|
||||
return <TextInput ref={ref} {...props} />
|
||||
})
|
||||
```
|
||||
|
||||
**Correct (ref as a regular prop):**
|
||||
|
||||
```tsx
|
||||
function ComposerInput({ ref, ...props }: Props & { ref?: React.Ref<TextInput> }) {
|
||||
return <TextInput ref={ref} {...props} />
|
||||
}
|
||||
```
|
||||
|
||||
**Incorrect (useContext in React 19):**
|
||||
|
||||
```tsx
|
||||
const value = useContext(MyContext)
|
||||
```
|
||||
|
||||
**Correct (use instead of useContext):**
|
||||
|
||||
```tsx
|
||||
const value = use(MyContext)
|
||||
```
|
||||
|
||||
`use()` can also be called conditionally, unlike `useContext()`.
|
||||
@@ -0,0 +1,191 @@
|
||||
---
|
||||
title: Define Generic Context Interfaces for Dependency Injection
|
||||
impact: HIGH
|
||||
impactDescription: enables dependency-injectable state across use-cases
|
||||
tags: composition, context, state, typescript, dependency-injection
|
||||
---
|
||||
|
||||
## Define Generic Context Interfaces for Dependency Injection
|
||||
|
||||
Define a **generic interface** for your component context with three parts:
|
||||
`state`, `actions`, and `meta`. This interface is a contract that any provider
|
||||
can implement—enabling the same UI components to work with completely different
|
||||
state implementations.
|
||||
|
||||
**Core principle:** Lift state, compose internals, make state
|
||||
dependency-injectable.
|
||||
|
||||
**Incorrect (UI coupled to specific state implementation):**
|
||||
|
||||
```tsx
|
||||
function ComposerInput() {
|
||||
// Tightly coupled to a specific hook
|
||||
const { input, setInput } = useChannelComposerState()
|
||||
return <TextInput value={input} onChangeText={setInput} />
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (generic interface enables dependency injection):**
|
||||
|
||||
```tsx
|
||||
// Define a GENERIC interface that any provider can implement
|
||||
interface ComposerState {
|
||||
input: string
|
||||
attachments: Attachment[]
|
||||
isSubmitting: boolean
|
||||
}
|
||||
|
||||
interface ComposerActions {
|
||||
update: (updater: (state: ComposerState) => ComposerState) => void
|
||||
submit: () => void
|
||||
}
|
||||
|
||||
interface ComposerMeta {
|
||||
inputRef: React.RefObject<TextInput>
|
||||
}
|
||||
|
||||
interface ComposerContextValue {
|
||||
state: ComposerState
|
||||
actions: ComposerActions
|
||||
meta: ComposerMeta
|
||||
}
|
||||
|
||||
const ComposerContext = createContext<ComposerContextValue | null>(null)
|
||||
```
|
||||
|
||||
**UI components consume the interface, not the implementation:**
|
||||
|
||||
```tsx
|
||||
function ComposerInput() {
|
||||
const {
|
||||
state,
|
||||
actions: { update },
|
||||
meta,
|
||||
} = use(ComposerContext)
|
||||
|
||||
// This component works with ANY provider that implements the interface
|
||||
return (
|
||||
<TextInput
|
||||
ref={meta.inputRef}
|
||||
value={state.input}
|
||||
onChangeText={(text) => update((s) => ({ ...s, input: text }))}
|
||||
/>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Different providers implement the same interface:**
|
||||
|
||||
```tsx
|
||||
// Provider A: Local state for ephemeral forms
|
||||
function ForwardMessageProvider({ children }: { children: React.ReactNode }) {
|
||||
const [state, setState] = useState(initialState)
|
||||
const inputRef = useRef(null)
|
||||
const submit = useForwardMessage()
|
||||
|
||||
return (
|
||||
<ComposerContext
|
||||
value={{
|
||||
state,
|
||||
actions: { update: setState, submit },
|
||||
meta: { inputRef },
|
||||
}}
|
||||
>
|
||||
{children}
|
||||
</ComposerContext>
|
||||
)
|
||||
}
|
||||
|
||||
// Provider B: Global synced state for channels
|
||||
function ChannelProvider({ channelId, children }: Props) {
|
||||
const { state, update, submit } = useGlobalChannel(channelId)
|
||||
const inputRef = useRef(null)
|
||||
|
||||
return (
|
||||
<ComposerContext
|
||||
value={{
|
||||
state,
|
||||
actions: { update, submit },
|
||||
meta: { inputRef },
|
||||
}}
|
||||
>
|
||||
{children}
|
||||
</ComposerContext>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**The same composed UI works with both:**
|
||||
|
||||
```tsx
|
||||
// Works with ForwardMessageProvider (local state)
|
||||
<ForwardMessageProvider>
|
||||
<Composer.Frame>
|
||||
<Composer.Input />
|
||||
<Composer.Submit />
|
||||
</Composer.Frame>
|
||||
</ForwardMessageProvider>
|
||||
|
||||
// Works with ChannelProvider (global synced state)
|
||||
<ChannelProvider channelId="abc">
|
||||
<Composer.Frame>
|
||||
<Composer.Input />
|
||||
<Composer.Submit />
|
||||
</Composer.Frame>
|
||||
</ChannelProvider>
|
||||
```
|
||||
|
||||
**Custom UI outside the component can access state and actions:**
|
||||
|
||||
The provider boundary is what matters—not the visual nesting. Components that
|
||||
need shared state don't have to be inside the `Composer.Frame`. They just need
|
||||
to be within the provider.
|
||||
|
||||
```tsx
|
||||
function ForwardMessageDialog() {
|
||||
return (
|
||||
<ForwardMessageProvider>
|
||||
<Dialog>
|
||||
{/* The composer UI */}
|
||||
<Composer.Frame>
|
||||
<Composer.Input placeholder="Add a message, if you'd like." />
|
||||
<Composer.Footer>
|
||||
<Composer.Formatting />
|
||||
<Composer.Emojis />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
|
||||
{/* Custom UI OUTSIDE the composer, but INSIDE the provider */}
|
||||
<MessagePreview />
|
||||
|
||||
{/* Actions at the bottom of the dialog */}
|
||||
<DialogActions>
|
||||
<CancelButton />
|
||||
<ForwardButton />
|
||||
</DialogActions>
|
||||
</Dialog>
|
||||
</ForwardMessageProvider>
|
||||
)
|
||||
}
|
||||
|
||||
// This button lives OUTSIDE Composer.Frame but can still submit based on its context!
|
||||
function ForwardButton() {
|
||||
const {
|
||||
actions: { submit },
|
||||
} = use(ComposerContext)
|
||||
return <Button onPress={submit}>Forward</Button>
|
||||
}
|
||||
|
||||
// This preview lives OUTSIDE Composer.Frame but can read composer's state!
|
||||
function MessagePreview() {
|
||||
const { state } = use(ComposerContext)
|
||||
return <Preview message={state.input} attachments={state.attachments} />
|
||||
}
|
||||
```
|
||||
|
||||
The `ForwardButton` and `MessagePreview` are not visually inside the composer
|
||||
box, but they can still access its state and actions. This is the power of
|
||||
lifting state into providers.
|
||||
|
||||
The UI is reusable bits you compose together. The state is dependency-injected
|
||||
by the provider. Swap the provider, keep the UI.
|
||||
@@ -0,0 +1,113 @@
|
||||
---
|
||||
title: Decouple State Management from UI
|
||||
impact: MEDIUM
|
||||
impactDescription: enables swapping state implementations without changing UI
|
||||
tags: composition, state, architecture
|
||||
---
|
||||
|
||||
## Decouple State Management from UI
|
||||
|
||||
The provider component should be the only place that knows how state is managed.
|
||||
UI components consume the context interface—they don't know if state comes from
|
||||
useState, Zustand, or a server sync.
|
||||
|
||||
**Incorrect (UI coupled to state implementation):**
|
||||
|
||||
```tsx
|
||||
function ChannelComposer({ channelId }: { channelId: string }) {
|
||||
// UI component knows about global state implementation
|
||||
const state = useGlobalChannelState(channelId)
|
||||
const { submit, updateInput } = useChannelSync(channelId)
|
||||
|
||||
return (
|
||||
<Composer.Frame>
|
||||
<Composer.Input
|
||||
value={state.input}
|
||||
onChange={(text) => sync.updateInput(text)}
|
||||
/>
|
||||
<Composer.Submit onPress={() => sync.submit()} />
|
||||
</Composer.Frame>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (state management isolated in provider):**
|
||||
|
||||
```tsx
|
||||
// Provider handles all state management details
|
||||
function ChannelProvider({
|
||||
channelId,
|
||||
children,
|
||||
}: {
|
||||
channelId: string
|
||||
children: React.ReactNode
|
||||
}) {
|
||||
const { state, update, submit } = useGlobalChannel(channelId)
|
||||
const inputRef = useRef(null)
|
||||
|
||||
return (
|
||||
<Composer.Provider
|
||||
state={state}
|
||||
actions={{ update, submit }}
|
||||
meta={{ inputRef }}
|
||||
>
|
||||
{children}
|
||||
</Composer.Provider>
|
||||
)
|
||||
}
|
||||
|
||||
// UI component only knows about the context interface
|
||||
function ChannelComposer() {
|
||||
return (
|
||||
<Composer.Frame>
|
||||
<Composer.Header />
|
||||
<Composer.Input />
|
||||
<Composer.Footer>
|
||||
<Composer.Submit />
|
||||
</Composer.Footer>
|
||||
</Composer.Frame>
|
||||
)
|
||||
}
|
||||
|
||||
// Usage
|
||||
function Channel({ channelId }: { channelId: string }) {
|
||||
return (
|
||||
<ChannelProvider channelId={channelId}>
|
||||
<ChannelComposer />
|
||||
</ChannelProvider>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Different providers, same UI:**
|
||||
|
||||
```tsx
|
||||
// Local state for ephemeral forms
|
||||
function ForwardMessageProvider({ children }) {
|
||||
const [state, setState] = useState(initialState)
|
||||
const forwardMessage = useForwardMessage()
|
||||
|
||||
return (
|
||||
<Composer.Provider
|
||||
state={state}
|
||||
actions={{ update: setState, submit: forwardMessage }}
|
||||
>
|
||||
{children}
|
||||
</Composer.Provider>
|
||||
)
|
||||
}
|
||||
|
||||
// Global synced state for channels
|
||||
function ChannelProvider({ channelId, children }) {
|
||||
const { state, update, submit } = useGlobalChannel(channelId)
|
||||
|
||||
return (
|
||||
<Composer.Provider state={state} actions={{ update, submit }}>
|
||||
{children}
|
||||
</Composer.Provider>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
The same `Composer.Input` component works with both providers because it only
|
||||
depends on the context interface, not the implementation.
|
||||
@@ -0,0 +1,125 @@
|
||||
---
|
||||
title: Lift State into Provider Components
|
||||
impact: HIGH
|
||||
impactDescription: enables state sharing outside component boundaries
|
||||
tags: composition, state, context, providers
|
||||
---
|
||||
|
||||
## Lift State into Provider Components
|
||||
|
||||
Move state management into dedicated provider components. This allows sibling
|
||||
components outside the main UI to access and modify state without prop drilling
|
||||
or awkward refs.
|
||||
|
||||
**Incorrect (state trapped inside component):**
|
||||
|
||||
```tsx
|
||||
function ForwardMessageComposer() {
|
||||
const [state, setState] = useState(initialState)
|
||||
const forwardMessage = useForwardMessage()
|
||||
|
||||
return (
|
||||
<Composer.Frame>
|
||||
<Composer.Input />
|
||||
<Composer.Footer />
|
||||
</Composer.Frame>
|
||||
)
|
||||
}
|
||||
|
||||
// Problem: How does this button access composer state?
|
||||
function ForwardMessageDialog() {
|
||||
return (
|
||||
<Dialog>
|
||||
<ForwardMessageComposer />
|
||||
<MessagePreview /> {/* Needs composer state */}
|
||||
<DialogActions>
|
||||
<CancelButton />
|
||||
<ForwardButton /> {/* Needs to call submit */}
|
||||
</DialogActions>
|
||||
</Dialog>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Incorrect (useEffect to sync state up):**
|
||||
|
||||
```tsx
|
||||
function ForwardMessageDialog() {
|
||||
const [input, setInput] = useState('')
|
||||
return (
|
||||
<Dialog>
|
||||
<ForwardMessageComposer onInputChange={setInput} />
|
||||
<MessagePreview input={input} />
|
||||
</Dialog>
|
||||
)
|
||||
}
|
||||
|
||||
function ForwardMessageComposer({ onInputChange }) {
|
||||
const [state, setState] = useState(initialState)
|
||||
useEffect(() => {
|
||||
onInputChange(state.input) // Sync on every change 😬
|
||||
}, [state.input])
|
||||
}
|
||||
```
|
||||
|
||||
**Incorrect (reading state from ref on submit):**
|
||||
|
||||
```tsx
|
||||
function ForwardMessageDialog() {
|
||||
const stateRef = useRef(null)
|
||||
return (
|
||||
<Dialog>
|
||||
<ForwardMessageComposer stateRef={stateRef} />
|
||||
<ForwardButton onPress={() => submit(stateRef.current)} />
|
||||
</Dialog>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (state lifted to provider):**
|
||||
|
||||
```tsx
|
||||
function ForwardMessageProvider({ children }: { children: React.ReactNode }) {
|
||||
const [state, setState] = useState(initialState)
|
||||
const forwardMessage = useForwardMessage()
|
||||
const inputRef = useRef(null)
|
||||
|
||||
return (
|
||||
<Composer.Provider
|
||||
state={state}
|
||||
actions={{ update: setState, submit: forwardMessage }}
|
||||
meta={{ inputRef }}
|
||||
>
|
||||
{children}
|
||||
</Composer.Provider>
|
||||
)
|
||||
}
|
||||
|
||||
function ForwardMessageDialog() {
|
||||
return (
|
||||
<ForwardMessageProvider>
|
||||
<Dialog>
|
||||
<ForwardMessageComposer />
|
||||
<MessagePreview /> {/* Custom components can access state and actions */}
|
||||
<DialogActions>
|
||||
<CancelButton />
|
||||
<ForwardButton /> {/* Custom components can access state and actions */}
|
||||
</DialogActions>
|
||||
</Dialog>
|
||||
</ForwardMessageProvider>
|
||||
)
|
||||
}
|
||||
|
||||
function ForwardButton() {
|
||||
const { actions } = use(Composer.Context)
|
||||
return <Button onPress={actions.submit}>Forward</Button>
|
||||
}
|
||||
```
|
||||
|
||||
The ForwardButton lives outside the Composer.Frame but still has access to the
|
||||
submit action because it's within the provider. Even though it's a one-off
|
||||
component, it can still access the composer's state and actions from outside the
|
||||
UI itself.
|
||||
|
||||
**Key insight:** Components that need shared state don't have to be visually
|
||||
nested inside each other—they just need to be within the same provider.
|
||||
File diff suppressed because it is too large
Load Diff
@@ -0,0 +1,123 @@
|
||||
# React Best Practices
|
||||
|
||||
A structured repository for creating and maintaining React Best Practices optimized for agents and LLMs.
|
||||
|
||||
## Structure
|
||||
|
||||
- `rules/` - Individual rule files (one per rule)
|
||||
- `_sections.md` - Section metadata (titles, impacts, descriptions)
|
||||
- `_template.md` - Template for creating new rules
|
||||
- `area-description.md` - Individual rule files
|
||||
- `src/` - Build scripts and utilities
|
||||
- `metadata.json` - Document metadata (version, organization, abstract)
|
||||
- __`AGENTS.md`__ - Compiled output (generated)
|
||||
- __`test-cases.json`__ - Test cases for LLM evaluation (generated)
|
||||
|
||||
## Getting Started
|
||||
|
||||
1. Install dependencies:
|
||||
```bash
|
||||
pnpm install
|
||||
```
|
||||
|
||||
2. Build AGENTS.md from rules:
|
||||
```bash
|
||||
pnpm build
|
||||
```
|
||||
|
||||
3. Validate rule files:
|
||||
```bash
|
||||
pnpm validate
|
||||
```
|
||||
|
||||
4. Extract test cases:
|
||||
```bash
|
||||
pnpm extract-tests
|
||||
```
|
||||
|
||||
## Creating a New Rule
|
||||
|
||||
1. Copy `rules/_template.md` to `rules/area-description.md`
|
||||
2. Choose the appropriate area prefix:
|
||||
- `async-` for Eliminating Waterfalls (Section 1)
|
||||
- `bundle-` for Bundle Size Optimization (Section 2)
|
||||
- `server-` for Server-Side Performance (Section 3)
|
||||
- `client-` for Client-Side Data Fetching (Section 4)
|
||||
- `rerender-` for Re-render Optimization (Section 5)
|
||||
- `rendering-` for Rendering Performance (Section 6)
|
||||
- `js-` for JavaScript Performance (Section 7)
|
||||
- `advanced-` for Advanced Patterns (Section 8)
|
||||
3. Fill in the frontmatter and content
|
||||
4. Ensure you have clear examples with explanations
|
||||
5. Run `pnpm build` to regenerate AGENTS.md and test-cases.json
|
||||
|
||||
## Rule File Structure
|
||||
|
||||
Each rule file should follow this structure:
|
||||
|
||||
```markdown
|
||||
---
|
||||
title: Rule Title Here
|
||||
impact: MEDIUM
|
||||
impactDescription: Optional description
|
||||
tags: tag1, tag2, tag3
|
||||
---
|
||||
|
||||
## Rule Title Here
|
||||
|
||||
Brief explanation of the rule and why it matters.
|
||||
|
||||
**Incorrect (description of what's wrong):**
|
||||
|
||||
```typescript
|
||||
// Bad code example
|
||||
```
|
||||
|
||||
**Correct (description of what's right):**
|
||||
|
||||
```typescript
|
||||
// Good code example
|
||||
```
|
||||
|
||||
Optional explanatory text after examples.
|
||||
|
||||
Reference: [Link](https://example.com)
|
||||
|
||||
## File Naming Convention
|
||||
|
||||
- Files starting with `_` are special (excluded from build)
|
||||
- Rule files: `area-description.md` (e.g., `async-parallel.md`)
|
||||
- Section is automatically inferred from filename prefix
|
||||
- Rules are sorted alphabetically by title within each section
|
||||
- IDs (e.g., 1.1, 1.2) are auto-generated during build
|
||||
|
||||
## Impact Levels
|
||||
|
||||
- `CRITICAL` - Highest priority, major performance gains
|
||||
- `HIGH` - Significant performance improvements
|
||||
- `MEDIUM-HIGH` - Moderate-high gains
|
||||
- `MEDIUM` - Moderate performance improvements
|
||||
- `LOW-MEDIUM` - Low-medium gains
|
||||
- `LOW` - Incremental improvements
|
||||
|
||||
## Scripts
|
||||
|
||||
- `pnpm build` - Compile rules into AGENTS.md
|
||||
- `pnpm validate` - Validate all rule files
|
||||
- `pnpm extract-tests` - Extract test cases for LLM evaluation
|
||||
- `pnpm dev` - Build and validate
|
||||
|
||||
## Contributing
|
||||
|
||||
When adding or modifying rules:
|
||||
|
||||
1. Use the correct filename prefix for your section
|
||||
2. Follow the `_template.md` structure
|
||||
3. Include clear bad/good examples with explanations
|
||||
4. Add appropriate tags
|
||||
5. Run `pnpm build` to regenerate AGENTS.md and test-cases.json
|
||||
6. Rules are automatically sorted by title - no need to manage numbers!
|
||||
|
||||
## Acknowledgments
|
||||
|
||||
Originally created by [@shuding](https://x.com/shuding) at [Vercel](https://vercel.com).
|
||||
@@ -0,0 +1,149 @@
|
||||
---
|
||||
name: vercel-react-best-practices
|
||||
description: React and Next.js performance optimization guidelines from Vercel Engineering. This skill should be used when writing, reviewing, or refactoring React/Next.js code to ensure optimal performance patterns. Triggers on tasks involving React components, Next.js pages, data fetching, bundle optimization, or performance improvements.
|
||||
license: MIT
|
||||
metadata:
|
||||
author: vercel
|
||||
version: "1.0.0"
|
||||
---
|
||||
|
||||
# Vercel React Best Practices
|
||||
|
||||
Comprehensive performance optimization guide for React and Next.js applications, maintained by Vercel. Contains 70 rules across 8 categories, prioritized by impact to guide automated refactoring and code generation.
|
||||
|
||||
## When to Apply
|
||||
|
||||
Reference these guidelines when:
|
||||
- Writing new React components or Next.js pages
|
||||
- Implementing data fetching (client or server-side)
|
||||
- Reviewing code for performance issues
|
||||
- Refactoring existing React/Next.js code
|
||||
- Optimizing bundle size or load times
|
||||
|
||||
## Rule Categories by Priority
|
||||
|
||||
| Priority | Category | Impact | Prefix |
|
||||
|----------|----------|--------|--------|
|
||||
| 1 | Eliminating Waterfalls | CRITICAL | `async-` |
|
||||
| 2 | Bundle Size Optimization | CRITICAL | `bundle-` |
|
||||
| 3 | Server-Side Performance | HIGH | `server-` |
|
||||
| 4 | Client-Side Data Fetching | MEDIUM-HIGH | `client-` |
|
||||
| 5 | Re-render Optimization | MEDIUM | `rerender-` |
|
||||
| 6 | Rendering Performance | MEDIUM | `rendering-` |
|
||||
| 7 | JavaScript Performance | LOW-MEDIUM | `js-` |
|
||||
| 8 | Advanced Patterns | LOW | `advanced-` |
|
||||
|
||||
## Quick Reference
|
||||
|
||||
### 1. Eliminating Waterfalls (CRITICAL)
|
||||
|
||||
- `async-cheap-condition-before-await` - Check cheap sync conditions before awaiting flags or remote values
|
||||
- `async-defer-await` - Move await into branches where actually used
|
||||
- `async-parallel` - Use Promise.all() for independent operations
|
||||
- `async-dependencies` - Use better-all for partial dependencies
|
||||
- `async-api-routes` - Start promises early, await late in API routes
|
||||
- `async-suspense-boundaries` - Use Suspense to stream content
|
||||
|
||||
### 2. Bundle Size Optimization (CRITICAL)
|
||||
|
||||
- `bundle-barrel-imports` - Import directly, avoid barrel files
|
||||
- `bundle-analyzable-paths` - Prefer statically analyzable import and file-system paths to avoid broad bundles and traces
|
||||
- `bundle-dynamic-imports` - Use next/dynamic for heavy components
|
||||
- `bundle-defer-third-party` - Load analytics/logging after hydration
|
||||
- `bundle-conditional` - Load modules only when feature is activated
|
||||
- `bundle-preload` - Preload on hover/focus for perceived speed
|
||||
|
||||
### 3. Server-Side Performance (HIGH)
|
||||
|
||||
- `server-auth-actions` - Authenticate server actions like API routes
|
||||
- `server-cache-react` - Use React.cache() for per-request deduplication
|
||||
- `server-cache-lru` - Use LRU cache for cross-request caching
|
||||
- `server-dedup-props` - Avoid duplicate serialization in RSC props
|
||||
- `server-hoist-static-io` - Hoist static I/O (fonts, logos) to module level
|
||||
- `server-no-shared-module-state` - Avoid module-level mutable request state in RSC/SSR
|
||||
- `server-serialization` - Minimize data passed to client components
|
||||
- `server-parallel-fetching` - Restructure components to parallelize fetches
|
||||
- `server-parallel-nested-fetching` - Chain nested fetches per item in Promise.all
|
||||
- `server-after-nonblocking` - Use after() for non-blocking operations
|
||||
|
||||
### 4. Client-Side Data Fetching (MEDIUM-HIGH)
|
||||
|
||||
- `client-swr-dedup` - Use SWR for automatic request deduplication
|
||||
- `client-event-listeners` - Deduplicate global event listeners
|
||||
- `client-passive-event-listeners` - Use passive listeners for scroll
|
||||
- `client-localstorage-schema` - Version and minimize localStorage data
|
||||
|
||||
### 5. Re-render Optimization (MEDIUM)
|
||||
|
||||
- `rerender-defer-reads` - Don't subscribe to state only used in callbacks
|
||||
- `rerender-memo` - Extract expensive work into memoized components
|
||||
- `rerender-memo-with-default-value` - Hoist default non-primitive props
|
||||
- `rerender-dependencies` - Use primitive dependencies in effects
|
||||
- `rerender-derived-state` - Subscribe to derived booleans, not raw values
|
||||
- `rerender-derived-state-no-effect` - Derive state during render, not effects
|
||||
- `rerender-functional-setstate` - Use functional setState for stable callbacks
|
||||
- `rerender-lazy-state-init` - Pass function to useState for expensive values
|
||||
- `rerender-simple-expression-in-memo` - Avoid memo for simple primitives
|
||||
- `rerender-split-combined-hooks` - Split hooks with independent dependencies
|
||||
- `rerender-move-effect-to-event` - Put interaction logic in event handlers
|
||||
- `rerender-transitions` - Use startTransition for non-urgent updates
|
||||
- `rerender-use-deferred-value` - Defer expensive renders to keep input responsive
|
||||
- `rerender-use-ref-transient-values` - Use refs for transient frequent values
|
||||
- `rerender-no-inline-components` - Don't define components inside components
|
||||
|
||||
### 6. Rendering Performance (MEDIUM)
|
||||
|
||||
- `rendering-animate-svg-wrapper` - Animate div wrapper, not SVG element
|
||||
- `rendering-content-visibility` - Use content-visibility for long lists
|
||||
- `rendering-hoist-jsx` - Extract static JSX outside components
|
||||
- `rendering-svg-precision` - Reduce SVG coordinate precision
|
||||
- `rendering-hydration-no-flicker` - Use inline script for client-only data
|
||||
- `rendering-hydration-suppress-warning` - Suppress expected mismatches
|
||||
- `rendering-activity` - Use Activity component for show/hide
|
||||
- `rendering-conditional-render` - Use ternary, not && for conditionals
|
||||
- `rendering-usetransition-loading` - Prefer useTransition for loading state
|
||||
- `rendering-resource-hints` - Use React DOM resource hints for preloading
|
||||
- `rendering-script-defer-async` - Use defer or async on script tags
|
||||
|
||||
### 7. JavaScript Performance (LOW-MEDIUM)
|
||||
|
||||
- `js-batch-dom-css` - Group CSS changes via classes or cssText
|
||||
- `js-index-maps` - Build Map for repeated lookups
|
||||
- `js-cache-property-access` - Cache object properties in loops
|
||||
- `js-cache-function-results` - Cache function results in module-level Map
|
||||
- `js-cache-storage` - Cache localStorage/sessionStorage reads
|
||||
- `js-combine-iterations` - Combine multiple filter/map into one loop
|
||||
- `js-length-check-first` - Check array length before expensive comparison
|
||||
- `js-early-exit` - Return early from functions
|
||||
- `js-hoist-regexp` - Hoist RegExp creation outside loops
|
||||
- `js-min-max-loop` - Use loop for min/max instead of sort
|
||||
- `js-set-map-lookups` - Use Set/Map for O(1) lookups
|
||||
- `js-tosorted-immutable` - Use toSorted() for immutability
|
||||
- `js-flatmap-filter` - Use flatMap to map and filter in one pass
|
||||
- `js-request-idle-callback` - Defer non-critical work to browser idle time
|
||||
|
||||
### 8. Advanced Patterns (LOW)
|
||||
|
||||
- `advanced-effect-event-deps` - Don't put `useEffectEvent` results in effect deps
|
||||
- `advanced-event-handler-refs` - Store event handlers in refs
|
||||
- `advanced-init-once` - Initialize app once per app load
|
||||
- `advanced-use-latest` - useLatest for stable callback refs
|
||||
|
||||
## How to Use
|
||||
|
||||
Read individual rule files for detailed explanations and code examples:
|
||||
|
||||
```
|
||||
rules/async-parallel.md
|
||||
rules/bundle-barrel-imports.md
|
||||
```
|
||||
|
||||
Each rule file contains:
|
||||
- Brief explanation of why it matters
|
||||
- Incorrect code example with explanation
|
||||
- Correct code example with explanation
|
||||
- Additional context and references
|
||||
|
||||
## Full Compiled Document
|
||||
|
||||
For the complete guide with all rules expanded: `AGENTS.md`
|
||||
@@ -0,0 +1,15 @@
|
||||
{
|
||||
"version": "1.0.0",
|
||||
"organization": "Vercel Engineering",
|
||||
"date": "January 2026",
|
||||
"abstract": "Comprehensive performance optimization guide for React and Next.js applications, designed for AI agents and LLMs. Contains 40+ rules across 8 categories, prioritized by impact from critical (eliminating waterfalls, reducing bundle size) to incremental (advanced patterns). Each rule includes detailed explanations, real-world examples comparing incorrect vs. correct implementations, and specific impact metrics to guide automated refactoring and code generation.",
|
||||
"references": [
|
||||
"https://react.dev",
|
||||
"https://nextjs.org",
|
||||
"https://swr.vercel.app",
|
||||
"https://github.com/shuding/better-all",
|
||||
"https://github.com/isaacs/node-lru-cache",
|
||||
"https://vercel.com/blog/how-we-optimized-package-imports-in-next-js",
|
||||
"https://vercel.com/blog/how-we-made-the-vercel-dashboard-twice-as-fast"
|
||||
]
|
||||
}
|
||||
@@ -0,0 +1,46 @@
|
||||
# Sections
|
||||
|
||||
This file defines all sections, their ordering, impact levels, and descriptions.
|
||||
The section ID (in parentheses) is the filename prefix used to group rules.
|
||||
|
||||
---
|
||||
|
||||
## 1. Eliminating Waterfalls (async)
|
||||
|
||||
**Impact:** CRITICAL
|
||||
**Description:** Waterfalls are the #1 performance killer. Each sequential await adds full network latency. Eliminating them yields the largest gains.
|
||||
|
||||
## 2. Bundle Size Optimization (bundle)
|
||||
|
||||
**Impact:** CRITICAL
|
||||
**Description:** Reducing initial bundle size improves Time to Interactive and Largest Contentful Paint.
|
||||
|
||||
## 3. Server-Side Performance (server)
|
||||
|
||||
**Impact:** HIGH
|
||||
**Description:** Optimizing server-side rendering and data fetching eliminates server-side waterfalls and reduces response times.
|
||||
|
||||
## 4. Client-Side Data Fetching (client)
|
||||
|
||||
**Impact:** MEDIUM-HIGH
|
||||
**Description:** Automatic deduplication and efficient data fetching patterns reduce redundant network requests.
|
||||
|
||||
## 5. Re-render Optimization (rerender)
|
||||
|
||||
**Impact:** MEDIUM
|
||||
**Description:** Reducing unnecessary re-renders minimizes wasted computation and improves UI responsiveness.
|
||||
|
||||
## 6. Rendering Performance (rendering)
|
||||
|
||||
**Impact:** MEDIUM
|
||||
**Description:** Optimizing the rendering process reduces the work the browser needs to do.
|
||||
|
||||
## 7. JavaScript Performance (js)
|
||||
|
||||
**Impact:** LOW-MEDIUM
|
||||
**Description:** Micro-optimizations for hot paths can add up to meaningful improvements.
|
||||
|
||||
## 8. Advanced Patterns (advanced)
|
||||
|
||||
**Impact:** LOW
|
||||
**Description:** Advanced patterns for specific cases that require careful implementation.
|
||||
@@ -0,0 +1,28 @@
|
||||
---
|
||||
title: Rule Title Here
|
||||
impact: MEDIUM
|
||||
impactDescription: Optional description of impact (e.g., "20-50% improvement")
|
||||
tags: tag1, tag2
|
||||
---
|
||||
|
||||
## Rule Title Here
|
||||
|
||||
**Impact: MEDIUM (optional impact description)**
|
||||
|
||||
Brief explanation of the rule and why it matters. This should be clear and concise, explaining the performance implications.
|
||||
|
||||
**Incorrect (description of what's wrong):**
|
||||
|
||||
```typescript
|
||||
// Bad code example here
|
||||
const bad = example()
|
||||
```
|
||||
|
||||
**Correct (description of what's right):**
|
||||
|
||||
```typescript
|
||||
// Good code example here
|
||||
const good = example()
|
||||
```
|
||||
|
||||
Reference: [Link to documentation or resource](https://example.com)
|
||||
@@ -0,0 +1,56 @@
|
||||
---
|
||||
title: Do Not Put Effect Events in Dependency Arrays
|
||||
impact: LOW
|
||||
impactDescription: avoids unnecessary effect re-runs and lint errors
|
||||
tags: advanced, hooks, useEffectEvent, dependencies, effects
|
||||
---
|
||||
|
||||
## Do Not Put Effect Events in Dependency Arrays
|
||||
|
||||
Effect Event functions do not have a stable identity. Their identity intentionally changes on every render. Do not include the function returned by `useEffectEvent` in a `useEffect` dependency array. Keep the actual reactive values as dependencies and call the Effect Event from inside the effect body or subscriptions created by that effect.
|
||||
|
||||
**Incorrect (Effect Event added as a dependency):**
|
||||
|
||||
```tsx
|
||||
import { useEffect, useEffectEvent } from 'react'
|
||||
|
||||
function ChatRoom({ roomId, onConnected }: {
|
||||
roomId: string
|
||||
onConnected: () => void
|
||||
}) {
|
||||
const handleConnected = useEffectEvent(onConnected)
|
||||
|
||||
useEffect(() => {
|
||||
const connection = createConnection(roomId)
|
||||
connection.on('connected', handleConnected)
|
||||
connection.connect()
|
||||
|
||||
return () => connection.disconnect()
|
||||
}, [roomId, handleConnected])
|
||||
}
|
||||
```
|
||||
|
||||
Including the Effect Event in dependencies makes the effect re-run every render and triggers the React Hooks lint rule.
|
||||
|
||||
**Correct (depend on reactive values, not the Effect Event):**
|
||||
|
||||
```tsx
|
||||
import { useEffect, useEffectEvent } from 'react'
|
||||
|
||||
function ChatRoom({ roomId, onConnected }: {
|
||||
roomId: string
|
||||
onConnected: () => void
|
||||
}) {
|
||||
const handleConnected = useEffectEvent(onConnected)
|
||||
|
||||
useEffect(() => {
|
||||
const connection = createConnection(roomId)
|
||||
connection.on('connected', handleConnected)
|
||||
connection.connect()
|
||||
|
||||
return () => connection.disconnect()
|
||||
}, [roomId])
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [React useEffectEvent: Effect Event in deps](https://react.dev/reference/react/useEffectEvent#effect-event-in-deps)
|
||||
@@ -0,0 +1,55 @@
|
||||
---
|
||||
title: Store Event Handlers in Refs
|
||||
impact: LOW
|
||||
impactDescription: stable subscriptions
|
||||
tags: advanced, hooks, refs, event-handlers, optimization
|
||||
---
|
||||
|
||||
## Store Event Handlers in Refs
|
||||
|
||||
Store callbacks in refs when used in effects that shouldn't re-subscribe on callback changes.
|
||||
|
||||
**Incorrect (re-subscribes on every render):**
|
||||
|
||||
```tsx
|
||||
function useWindowEvent(event: string, handler: (e) => void) {
|
||||
useEffect(() => {
|
||||
window.addEventListener(event, handler)
|
||||
return () => window.removeEventListener(event, handler)
|
||||
}, [event, handler])
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (stable subscription):**
|
||||
|
||||
```tsx
|
||||
function useWindowEvent(event: string, handler: (e) => void) {
|
||||
const handlerRef = useRef(handler)
|
||||
useEffect(() => {
|
||||
handlerRef.current = handler
|
||||
}, [handler])
|
||||
|
||||
useEffect(() => {
|
||||
const listener = (e) => handlerRef.current(e)
|
||||
window.addEventListener(event, listener)
|
||||
return () => window.removeEventListener(event, listener)
|
||||
}, [event])
|
||||
}
|
||||
```
|
||||
|
||||
**Alternative: use `useEffectEvent` if you're on latest React:**
|
||||
|
||||
```tsx
|
||||
import { useEffectEvent } from 'react'
|
||||
|
||||
function useWindowEvent(event: string, handler: (e) => void) {
|
||||
const onEvent = useEffectEvent(handler)
|
||||
|
||||
useEffect(() => {
|
||||
window.addEventListener(event, onEvent)
|
||||
return () => window.removeEventListener(event, onEvent)
|
||||
}, [event])
|
||||
}
|
||||
```
|
||||
|
||||
`useEffectEvent` provides a cleaner API for the same pattern: it creates a stable function reference that always calls the latest version of the handler.
|
||||
@@ -0,0 +1,42 @@
|
||||
---
|
||||
title: Initialize App Once, Not Per Mount
|
||||
impact: LOW-MEDIUM
|
||||
impactDescription: avoids duplicate init in development
|
||||
tags: initialization, useEffect, app-startup, side-effects
|
||||
---
|
||||
|
||||
## Initialize App Once, Not Per Mount
|
||||
|
||||
Do not put app-wide initialization that must run once per app load inside `useEffect([])` of a component. Components can remount and effects will re-run. Use a module-level guard or top-level init in the entry module instead.
|
||||
|
||||
**Incorrect (runs twice in dev, re-runs on remount):**
|
||||
|
||||
```tsx
|
||||
function Comp() {
|
||||
useEffect(() => {
|
||||
loadFromStorage()
|
||||
checkAuthToken()
|
||||
}, [])
|
||||
|
||||
// ...
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (once per app load):**
|
||||
|
||||
```tsx
|
||||
let didInit = false
|
||||
|
||||
function Comp() {
|
||||
useEffect(() => {
|
||||
if (didInit) return
|
||||
didInit = true
|
||||
loadFromStorage()
|
||||
checkAuthToken()
|
||||
}, [])
|
||||
|
||||
// ...
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [Initializing the application](https://react.dev/learn/you-might-not-need-an-effect#initializing-the-application)
|
||||
@@ -0,0 +1,39 @@
|
||||
---
|
||||
title: useEffectEvent for Stable Callback Refs
|
||||
impact: LOW
|
||||
impactDescription: prevents effect re-runs
|
||||
tags: advanced, hooks, useEffectEvent, refs, optimization
|
||||
---
|
||||
|
||||
## useEffectEvent for Stable Callback Refs
|
||||
|
||||
Access latest values in callbacks without adding them to dependency arrays. Prevents effect re-runs while avoiding stale closures.
|
||||
|
||||
**Incorrect (effect re-runs on every callback change):**
|
||||
|
||||
```tsx
|
||||
function SearchInput({ onSearch }: { onSearch: (q: string) => void }) {
|
||||
const [query, setQuery] = useState('')
|
||||
|
||||
useEffect(() => {
|
||||
const timeout = setTimeout(() => onSearch(query), 300)
|
||||
return () => clearTimeout(timeout)
|
||||
}, [query, onSearch])
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (using React's useEffectEvent):**
|
||||
|
||||
```tsx
|
||||
import { useEffectEvent } from 'react';
|
||||
|
||||
function SearchInput({ onSearch }: { onSearch: (q: string) => void }) {
|
||||
const [query, setQuery] = useState('')
|
||||
const onSearchEvent = useEffectEvent(onSearch)
|
||||
|
||||
useEffect(() => {
|
||||
const timeout = setTimeout(() => onSearchEvent(query), 300)
|
||||
return () => clearTimeout(timeout)
|
||||
}, [query])
|
||||
}
|
||||
```
|
||||
@@ -0,0 +1,38 @@
|
||||
---
|
||||
title: Prevent Waterfall Chains in API Routes
|
||||
impact: CRITICAL
|
||||
impactDescription: 2-10× improvement
|
||||
tags: api-routes, server-actions, waterfalls, parallelization
|
||||
---
|
||||
|
||||
## Prevent Waterfall Chains in API Routes
|
||||
|
||||
In API routes and Server Actions, start independent operations immediately, even if you don't await them yet.
|
||||
|
||||
**Incorrect (config waits for auth, data waits for both):**
|
||||
|
||||
```typescript
|
||||
export async function GET(request: Request) {
|
||||
const session = await auth()
|
||||
const config = await fetchConfig()
|
||||
const data = await fetchData(session.user.id)
|
||||
return Response.json({ data, config })
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (auth and config start immediately):**
|
||||
|
||||
```typescript
|
||||
export async function GET(request: Request) {
|
||||
const sessionPromise = auth()
|
||||
const configPromise = fetchConfig()
|
||||
const session = await sessionPromise
|
||||
const [config, data] = await Promise.all([
|
||||
configPromise,
|
||||
fetchData(session.user.id)
|
||||
])
|
||||
return Response.json({ data, config })
|
||||
}
|
||||
```
|
||||
|
||||
For operations with more complex dependency chains, use `better-all` to automatically maximize parallelism (see Dependency-Based Parallelization).
|
||||
+37
@@ -0,0 +1,37 @@
|
||||
---
|
||||
title: Check Cheap Conditions Before Async Flags
|
||||
impact: HIGH
|
||||
impactDescription: avoids unnecessary async work when a synchronous guard already fails
|
||||
tags: async, await, feature-flags, short-circuit, conditional
|
||||
---
|
||||
|
||||
## Check Cheap Conditions Before Async Flags
|
||||
|
||||
When a branch uses `await` for a flag or remote value and also requires a **cheap synchronous** condition (local props, request metadata, already-loaded state), evaluate the cheap condition **first**. Otherwise you pay for the async call even when the compound condition can never be true.
|
||||
|
||||
This is a specialization of [Defer Await Until Needed](./async-defer-await.md) for `flag && cheapCondition` style checks.
|
||||
|
||||
**Incorrect:**
|
||||
|
||||
```typescript
|
||||
const someFlag = await getFlag()
|
||||
|
||||
if (someFlag && someCondition) {
|
||||
// ...
|
||||
}
|
||||
```
|
||||
|
||||
**Correct:**
|
||||
|
||||
```typescript
|
||||
if (someCondition) {
|
||||
const someFlag = await getFlag()
|
||||
if (someFlag) {
|
||||
// ...
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
This matters when `getFlag` hits the network, a feature-flag service, or `React.cache` / DB work: skipping it when `someCondition` is false removes that cost on the cold path.
|
||||
|
||||
Keep the original order if `someCondition` is expensive, depends on the flag, or you must run side effects in a fixed order.
|
||||
@@ -0,0 +1,82 @@
|
||||
---
|
||||
title: Defer Await Until Needed
|
||||
impact: HIGH
|
||||
impactDescription: avoids blocking unused code paths
|
||||
tags: async, await, conditional, optimization
|
||||
---
|
||||
|
||||
## Defer Await Until Needed
|
||||
|
||||
Move `await` operations into the branches where they're actually used to avoid blocking code paths that don't need them.
|
||||
|
||||
**Incorrect (blocks both branches):**
|
||||
|
||||
```typescript
|
||||
async function handleRequest(userId: string, skipProcessing: boolean) {
|
||||
const userData = await fetchUserData(userId)
|
||||
|
||||
if (skipProcessing) {
|
||||
// Returns immediately but still waited for userData
|
||||
return { skipped: true }
|
||||
}
|
||||
|
||||
// Only this branch uses userData
|
||||
return processUserData(userData)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (only blocks when needed):**
|
||||
|
||||
```typescript
|
||||
async function handleRequest(userId: string, skipProcessing: boolean) {
|
||||
if (skipProcessing) {
|
||||
// Returns immediately without waiting
|
||||
return { skipped: true }
|
||||
}
|
||||
|
||||
// Fetch only when needed
|
||||
const userData = await fetchUserData(userId)
|
||||
return processUserData(userData)
|
||||
}
|
||||
```
|
||||
|
||||
**Another example (early return optimization):**
|
||||
|
||||
```typescript
|
||||
// Incorrect: always fetches permissions
|
||||
async function updateResource(resourceId: string, userId: string) {
|
||||
const permissions = await fetchPermissions(userId)
|
||||
const resource = await getResource(resourceId)
|
||||
|
||||
if (!resource) {
|
||||
return { error: 'Not found' }
|
||||
}
|
||||
|
||||
if (!permissions.canEdit) {
|
||||
return { error: 'Forbidden' }
|
||||
}
|
||||
|
||||
return await updateResourceData(resource, permissions)
|
||||
}
|
||||
|
||||
// Correct: fetches only when needed
|
||||
async function updateResource(resourceId: string, userId: string) {
|
||||
const resource = await getResource(resourceId)
|
||||
|
||||
if (!resource) {
|
||||
return { error: 'Not found' }
|
||||
}
|
||||
|
||||
const permissions = await fetchPermissions(userId)
|
||||
|
||||
if (!permissions.canEdit) {
|
||||
return { error: 'Forbidden' }
|
||||
}
|
||||
|
||||
return await updateResourceData(resource, permissions)
|
||||
}
|
||||
```
|
||||
|
||||
This optimization is especially valuable when the skipped branch is frequently taken, or when the deferred operation is expensive.
|
||||
|
||||
For `await getFlag()` combined with a cheap synchronous guard (`flag && someCondition`), see [Check Cheap Conditions Before Async Flags](./async-cheap-condition-before-await.md).
|
||||
@@ -0,0 +1,51 @@
|
||||
---
|
||||
title: Dependency-Based Parallelization
|
||||
impact: CRITICAL
|
||||
impactDescription: 2-10× improvement
|
||||
tags: async, parallelization, dependencies, better-all
|
||||
---
|
||||
|
||||
## Dependency-Based Parallelization
|
||||
|
||||
For operations with partial dependencies, use `better-all` to maximize parallelism. It automatically starts each task at the earliest possible moment.
|
||||
|
||||
**Incorrect (profile waits for config unnecessarily):**
|
||||
|
||||
```typescript
|
||||
const [user, config] = await Promise.all([
|
||||
fetchUser(),
|
||||
fetchConfig()
|
||||
])
|
||||
const profile = await fetchProfile(user.id)
|
||||
```
|
||||
|
||||
**Correct (config and profile run in parallel):**
|
||||
|
||||
```typescript
|
||||
import { all } from 'better-all'
|
||||
|
||||
const { user, config, profile } = await all({
|
||||
async user() { return fetchUser() },
|
||||
async config() { return fetchConfig() },
|
||||
async profile() {
|
||||
return fetchProfile((await this.$.user).id)
|
||||
}
|
||||
})
|
||||
```
|
||||
|
||||
**Alternative without extra dependencies:**
|
||||
|
||||
We can also create all the promises first, and do `Promise.all()` at the end.
|
||||
|
||||
```typescript
|
||||
const userPromise = fetchUser()
|
||||
const profilePromise = userPromise.then(user => fetchProfile(user.id))
|
||||
|
||||
const [user, config, profile] = await Promise.all([
|
||||
userPromise,
|
||||
fetchConfig(),
|
||||
profilePromise
|
||||
])
|
||||
```
|
||||
|
||||
Reference: [https://github.com/shuding/better-all](https://github.com/shuding/better-all)
|
||||
@@ -0,0 +1,28 @@
|
||||
---
|
||||
title: Promise.all() for Independent Operations
|
||||
impact: CRITICAL
|
||||
impactDescription: 2-10× improvement
|
||||
tags: async, parallelization, promises, waterfalls
|
||||
---
|
||||
|
||||
## Promise.all() for Independent Operations
|
||||
|
||||
When async operations have no interdependencies, execute them concurrently using `Promise.all()`.
|
||||
|
||||
**Incorrect (sequential execution, 3 round trips):**
|
||||
|
||||
```typescript
|
||||
const user = await fetchUser()
|
||||
const posts = await fetchPosts()
|
||||
const comments = await fetchComments()
|
||||
```
|
||||
|
||||
**Correct (parallel execution, 1 round trip):**
|
||||
|
||||
```typescript
|
||||
const [user, posts, comments] = await Promise.all([
|
||||
fetchUser(),
|
||||
fetchPosts(),
|
||||
fetchComments()
|
||||
])
|
||||
```
|
||||
@@ -0,0 +1,99 @@
|
||||
---
|
||||
title: Strategic Suspense Boundaries
|
||||
impact: HIGH
|
||||
impactDescription: faster initial paint
|
||||
tags: async, suspense, streaming, layout-shift
|
||||
---
|
||||
|
||||
## Strategic Suspense Boundaries
|
||||
|
||||
Instead of awaiting data in async components before returning JSX, use Suspense boundaries to show the wrapper UI faster while data loads.
|
||||
|
||||
**Incorrect (wrapper blocked by data fetching):**
|
||||
|
||||
```tsx
|
||||
async function Page() {
|
||||
const data = await fetchData() // Blocks entire page
|
||||
|
||||
return (
|
||||
<div>
|
||||
<div>Sidebar</div>
|
||||
<div>Header</div>
|
||||
<div>
|
||||
<DataDisplay data={data} />
|
||||
</div>
|
||||
<div>Footer</div>
|
||||
</div>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
The entire layout waits for data even though only the middle section needs it.
|
||||
|
||||
**Correct (wrapper shows immediately, data streams in):**
|
||||
|
||||
```tsx
|
||||
function Page() {
|
||||
return (
|
||||
<div>
|
||||
<div>Sidebar</div>
|
||||
<div>Header</div>
|
||||
<div>
|
||||
<Suspense fallback={<Skeleton />}>
|
||||
<DataDisplay />
|
||||
</Suspense>
|
||||
</div>
|
||||
<div>Footer</div>
|
||||
</div>
|
||||
)
|
||||
}
|
||||
|
||||
async function DataDisplay() {
|
||||
const data = await fetchData() // Only blocks this component
|
||||
return <div>{data.content}</div>
|
||||
}
|
||||
```
|
||||
|
||||
Sidebar, Header, and Footer render immediately. Only DataDisplay waits for data.
|
||||
|
||||
**Alternative (share promise across components):**
|
||||
|
||||
```tsx
|
||||
function Page() {
|
||||
// Start fetch immediately, but don't await
|
||||
const dataPromise = fetchData()
|
||||
|
||||
return (
|
||||
<div>
|
||||
<div>Sidebar</div>
|
||||
<div>Header</div>
|
||||
<Suspense fallback={<Skeleton />}>
|
||||
<DataDisplay dataPromise={dataPromise} />
|
||||
<DataSummary dataPromise={dataPromise} />
|
||||
</Suspense>
|
||||
<div>Footer</div>
|
||||
</div>
|
||||
)
|
||||
}
|
||||
|
||||
function DataDisplay({ dataPromise }: { dataPromise: Promise<Data> }) {
|
||||
const data = use(dataPromise) // Unwraps the promise
|
||||
return <div>{data.content}</div>
|
||||
}
|
||||
|
||||
function DataSummary({ dataPromise }: { dataPromise: Promise<Data> }) {
|
||||
const data = use(dataPromise) // Reuses the same promise
|
||||
return <div>{data.summary}</div>
|
||||
}
|
||||
```
|
||||
|
||||
Both components share the same promise, so only one fetch occurs. Layout renders immediately while both components wait together.
|
||||
|
||||
**When NOT to use this pattern:**
|
||||
|
||||
- Critical data needed for layout decisions (affects positioning)
|
||||
- SEO-critical content above the fold
|
||||
- Small, fast queries where suspense overhead isn't worth it
|
||||
- When you want to avoid layout shift (loading → content jump)
|
||||
|
||||
**Trade-off:** Faster initial paint vs potential layout shift. Choose based on your UX priorities.
|
||||
@@ -0,0 +1,63 @@
|
||||
---
|
||||
title: Prefer Statically Analyzable Paths
|
||||
impact: HIGH
|
||||
impactDescription: avoids accidental broad bundles and file traces
|
||||
tags: bundle, nextjs, vite, webpack, rollup, esbuild, path
|
||||
---
|
||||
|
||||
## Prefer Statically Analyzable Paths
|
||||
|
||||
Build tools work best when import and file-system paths are obvious at build time. If you hide the real path inside a variable or compose it too dynamically, the tool either has to include a broad set of possible files, warn that it cannot analyze the import, or widen file tracing to stay safe.
|
||||
|
||||
Prefer explicit maps or literal paths so the set of reachable files stays narrow and predictable. This is the same rule whether you are choosing modules with `import()` or reading files in server/build code.
|
||||
|
||||
When analysis becomes too broad, the cost is real:
|
||||
- Larger server bundles
|
||||
- Slower builds
|
||||
- Worse cold starts
|
||||
- More memory use
|
||||
|
||||
### Import Paths
|
||||
|
||||
**Incorrect (the bundler cannot tell what may be imported):**
|
||||
|
||||
```ts
|
||||
const PAGE_MODULES = {
|
||||
home: './pages/home',
|
||||
settings: './pages/settings',
|
||||
} as const
|
||||
|
||||
const Page = await import(PAGE_MODULES[pageName])
|
||||
```
|
||||
|
||||
**Correct (use an explicit map of allowed modules):**
|
||||
|
||||
```ts
|
||||
const PAGE_MODULES = {
|
||||
home: () => import('./pages/home'),
|
||||
settings: () => import('./pages/settings'),
|
||||
} as const
|
||||
|
||||
const Page = await PAGE_MODULES[pageName]()
|
||||
```
|
||||
|
||||
### File-System Paths
|
||||
|
||||
**Incorrect (a 2-value enum still hides the final path from static analysis):**
|
||||
|
||||
```ts
|
||||
const baseDir = path.join(process.cwd(), 'content/' + contentKind)
|
||||
```
|
||||
|
||||
**Correct (make each final path literal at the callsite):**
|
||||
|
||||
```ts
|
||||
const baseDir =
|
||||
kind === ContentKind.Blog
|
||||
? path.join(process.cwd(), 'content/blog')
|
||||
: path.join(process.cwd(), 'content/docs')
|
||||
```
|
||||
|
||||
In Next.js server code, this matters for output file tracing too. `path.join(process.cwd(), someVar)` can widen the traced file set because Next.js statically analyze `import`, `require`, and `fs` usage.
|
||||
|
||||
Reference: [Next.js output](https://nextjs.org/docs/app/api-reference/config/next-config-js/output), [Next.js dynamic imports](https://nextjs.org/learn/seo/dynamic-imports), [Vite features](https://vite.dev/guide/features.html), [esbuild API](https://esbuild.github.io/api/), [Rollup dynamic import vars](https://www.npmjs.com/package/@rollup/plugin-dynamic-import-vars), [Webpack dependency management](https://webpack.js.org/guides/dependency-management/)
|
||||
@@ -0,0 +1,60 @@
|
||||
---
|
||||
title: Avoid Barrel File Imports
|
||||
impact: CRITICAL
|
||||
impactDescription: 200-800ms import cost, slow builds
|
||||
tags: bundle, imports, tree-shaking, barrel-files, performance
|
||||
---
|
||||
|
||||
## Avoid Barrel File Imports
|
||||
|
||||
Import directly from source files instead of barrel files to avoid loading thousands of unused modules. **Barrel files** are entry points that re-export multiple modules (e.g., `index.js` that does `export * from './module'`).
|
||||
|
||||
Popular icon and component libraries can have **up to 10,000 re-exports** in their entry file. For many React packages, **it takes 200-800ms just to import them**, affecting both development speed and production cold starts.
|
||||
|
||||
**Why tree-shaking doesn't help:** When a library is marked as external (not bundled), the bundler can't optimize it. If you bundle it to enable tree-shaking, builds become substantially slower analyzing the entire module graph.
|
||||
|
||||
**Incorrect (imports entire library):**
|
||||
|
||||
```tsx
|
||||
import { Check, X, Menu } from 'lucide-react'
|
||||
// Loads 1,583 modules, takes ~2.8s extra in dev
|
||||
// Runtime cost: 200-800ms on every cold start
|
||||
|
||||
import { Button, TextField } from '@mui/material'
|
||||
// Loads 2,225 modules, takes ~4.2s extra in dev
|
||||
```
|
||||
|
||||
**Correct - Next.js 13.5+ (recommended):**
|
||||
|
||||
```js
|
||||
// next.config.js - automatically optimizes barrel imports at build time
|
||||
module.exports = {
|
||||
experimental: {
|
||||
optimizePackageImports: ['lucide-react', '@mui/material']
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
```tsx
|
||||
// Keep the standard imports - Next.js transforms them to direct imports
|
||||
import { Check, X, Menu } from 'lucide-react'
|
||||
// Full TypeScript support, no manual path wrangling
|
||||
```
|
||||
|
||||
This is the recommended approach because it preserves TypeScript type safety and editor autocompletion while still eliminating the barrel import cost.
|
||||
|
||||
**Correct - Direct imports (non-Next.js projects):**
|
||||
|
||||
```tsx
|
||||
import Button from '@mui/material/Button'
|
||||
import TextField from '@mui/material/TextField'
|
||||
// Loads only what you use
|
||||
```
|
||||
|
||||
> **TypeScript warning:** Some libraries (notably `lucide-react`) don't ship `.d.ts` files for their deep import paths. Importing from `lucide-react/dist/esm/icons/check` resolves to an implicit `any` type, causing errors under `strict` or `noImplicitAny`. Prefer `optimizePackageImports` when available, or verify the library exports types for its subpaths before using direct imports.
|
||||
|
||||
These optimizations provide 15-70% faster dev boot, 28% faster builds, 40% faster cold starts, and significantly faster HMR.
|
||||
|
||||
Libraries commonly affected: `lucide-react`, `@mui/material`, `@mui/icons-material`, `@tabler/icons-react`, `react-icons`, `@headlessui/react`, `@radix-ui/react-*`, `lodash`, `ramda`, `date-fns`, `rxjs`, `react-use`.
|
||||
|
||||
Reference: [How we optimized package imports in Next.js](https://vercel.com/blog/how-we-optimized-package-imports-in-next-js)
|
||||
@@ -0,0 +1,31 @@
|
||||
---
|
||||
title: Conditional Module Loading
|
||||
impact: HIGH
|
||||
impactDescription: loads large data only when needed
|
||||
tags: bundle, conditional-loading, lazy-loading
|
||||
---
|
||||
|
||||
## Conditional Module Loading
|
||||
|
||||
Load large data or modules only when a feature is activated.
|
||||
|
||||
**Example (lazy-load animation frames):**
|
||||
|
||||
```tsx
|
||||
function AnimationPlayer({ enabled, setEnabled }: { enabled: boolean; setEnabled: React.Dispatch<React.SetStateAction<boolean>> }) {
|
||||
const [frames, setFrames] = useState<Frame[] | null>(null)
|
||||
|
||||
useEffect(() => {
|
||||
if (enabled && !frames && typeof window !== 'undefined') {
|
||||
import('./animation-frames.js')
|
||||
.then(mod => setFrames(mod.frames))
|
||||
.catch(() => setEnabled(false))
|
||||
}
|
||||
}, [enabled, frames, setEnabled])
|
||||
|
||||
if (!frames) return <Skeleton />
|
||||
return <Canvas frames={frames} />
|
||||
}
|
||||
```
|
||||
|
||||
The `typeof window !== 'undefined'` check prevents bundling this module for SSR, optimizing server bundle size and build speed.
|
||||
@@ -0,0 +1,49 @@
|
||||
---
|
||||
title: Defer Non-Critical Third-Party Libraries
|
||||
impact: MEDIUM
|
||||
impactDescription: loads after hydration
|
||||
tags: bundle, third-party, analytics, defer
|
||||
---
|
||||
|
||||
## Defer Non-Critical Third-Party Libraries
|
||||
|
||||
Analytics, logging, and error tracking don't block user interaction. Load them after hydration.
|
||||
|
||||
**Incorrect (blocks initial bundle):**
|
||||
|
||||
```tsx
|
||||
import { Analytics } from '@vercel/analytics/react'
|
||||
|
||||
export default function RootLayout({ children }) {
|
||||
return (
|
||||
<html>
|
||||
<body>
|
||||
{children}
|
||||
<Analytics />
|
||||
</body>
|
||||
</html>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (loads after hydration):**
|
||||
|
||||
```tsx
|
||||
import dynamic from 'next/dynamic'
|
||||
|
||||
const Analytics = dynamic(
|
||||
() => import('@vercel/analytics/react').then(m => m.Analytics),
|
||||
{ ssr: false }
|
||||
)
|
||||
|
||||
export default function RootLayout({ children }) {
|
||||
return (
|
||||
<html>
|
||||
<body>
|
||||
{children}
|
||||
<Analytics />
|
||||
</body>
|
||||
</html>
|
||||
)
|
||||
}
|
||||
```
|
||||
@@ -0,0 +1,35 @@
|
||||
---
|
||||
title: Dynamic Imports for Heavy Components
|
||||
impact: CRITICAL
|
||||
impactDescription: directly affects TTI and LCP
|
||||
tags: bundle, dynamic-import, code-splitting, next-dynamic
|
||||
---
|
||||
|
||||
## Dynamic Imports for Heavy Components
|
||||
|
||||
Use `next/dynamic` to lazy-load large components not needed on initial render.
|
||||
|
||||
**Incorrect (Monaco bundles with main chunk ~300KB):**
|
||||
|
||||
```tsx
|
||||
import { MonacoEditor } from './monaco-editor'
|
||||
|
||||
function CodePanel({ code }: { code: string }) {
|
||||
return <MonacoEditor value={code} />
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (Monaco loads on demand):**
|
||||
|
||||
```tsx
|
||||
import dynamic from 'next/dynamic'
|
||||
|
||||
const MonacoEditor = dynamic(
|
||||
() => import('./monaco-editor').then(m => m.MonacoEditor),
|
||||
{ ssr: false }
|
||||
)
|
||||
|
||||
function CodePanel({ code }: { code: string }) {
|
||||
return <MonacoEditor value={code} />
|
||||
}
|
||||
```
|
||||
@@ -0,0 +1,50 @@
|
||||
---
|
||||
title: Preload Based on User Intent
|
||||
impact: MEDIUM
|
||||
impactDescription: reduces perceived latency
|
||||
tags: bundle, preload, user-intent, hover
|
||||
---
|
||||
|
||||
## Preload Based on User Intent
|
||||
|
||||
Preload heavy bundles before they're needed to reduce perceived latency.
|
||||
|
||||
**Example (preload on hover/focus):**
|
||||
|
||||
```tsx
|
||||
function EditorButton({ onClick }: { onClick: () => void }) {
|
||||
const preload = () => {
|
||||
if (typeof window !== 'undefined') {
|
||||
void import('./monaco-editor')
|
||||
}
|
||||
}
|
||||
|
||||
return (
|
||||
<button
|
||||
onMouseEnter={preload}
|
||||
onFocus={preload}
|
||||
onClick={onClick}
|
||||
>
|
||||
Open Editor
|
||||
</button>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Example (preload when feature flag is enabled):**
|
||||
|
||||
```tsx
|
||||
function FlagsProvider({ children, flags }: Props) {
|
||||
useEffect(() => {
|
||||
if (flags.editorEnabled && typeof window !== 'undefined') {
|
||||
void import('./monaco-editor').then(mod => mod.init())
|
||||
}
|
||||
}, [flags.editorEnabled])
|
||||
|
||||
return <FlagsContext.Provider value={flags}>
|
||||
{children}
|
||||
</FlagsContext.Provider>
|
||||
}
|
||||
```
|
||||
|
||||
The `typeof window !== 'undefined'` check prevents bundling preloaded modules for SSR, optimizing server bundle size and build speed.
|
||||
@@ -0,0 +1,74 @@
|
||||
---
|
||||
title: Deduplicate Global Event Listeners
|
||||
impact: LOW
|
||||
impactDescription: single listener for N components
|
||||
tags: client, swr, event-listeners, subscription
|
||||
---
|
||||
|
||||
## Deduplicate Global Event Listeners
|
||||
|
||||
Use `useSWRSubscription()` to share global event listeners across component instances.
|
||||
|
||||
**Incorrect (N instances = N listeners):**
|
||||
|
||||
```tsx
|
||||
function useKeyboardShortcut(key: string, callback: () => void) {
|
||||
useEffect(() => {
|
||||
const handler = (e: KeyboardEvent) => {
|
||||
if (e.metaKey && e.key === key) {
|
||||
callback()
|
||||
}
|
||||
}
|
||||
window.addEventListener('keydown', handler)
|
||||
return () => window.removeEventListener('keydown', handler)
|
||||
}, [key, callback])
|
||||
}
|
||||
```
|
||||
|
||||
When using the `useKeyboardShortcut` hook multiple times, each instance will register a new listener.
|
||||
|
||||
**Correct (N instances = 1 listener):**
|
||||
|
||||
```tsx
|
||||
import useSWRSubscription from 'swr/subscription'
|
||||
|
||||
// Module-level Map to track callbacks per key
|
||||
const keyCallbacks = new Map<string, Set<() => void>>()
|
||||
|
||||
function useKeyboardShortcut(key: string, callback: () => void) {
|
||||
// Register this callback in the Map
|
||||
useEffect(() => {
|
||||
if (!keyCallbacks.has(key)) {
|
||||
keyCallbacks.set(key, new Set())
|
||||
}
|
||||
keyCallbacks.get(key)!.add(callback)
|
||||
|
||||
return () => {
|
||||
const set = keyCallbacks.get(key)
|
||||
if (set) {
|
||||
set.delete(callback)
|
||||
if (set.size === 0) {
|
||||
keyCallbacks.delete(key)
|
||||
}
|
||||
}
|
||||
}
|
||||
}, [key, callback])
|
||||
|
||||
useSWRSubscription('global-keydown', () => {
|
||||
const handler = (e: KeyboardEvent) => {
|
||||
if (e.metaKey && keyCallbacks.has(e.key)) {
|
||||
keyCallbacks.get(e.key)!.forEach(cb => cb())
|
||||
}
|
||||
}
|
||||
window.addEventListener('keydown', handler)
|
||||
return () => window.removeEventListener('keydown', handler)
|
||||
})
|
||||
}
|
||||
|
||||
function Profile() {
|
||||
// Multiple shortcuts will share the same listener
|
||||
useKeyboardShortcut('p', () => { /* ... */ })
|
||||
useKeyboardShortcut('k', () => { /* ... */ })
|
||||
// ...
|
||||
}
|
||||
```
|
||||
@@ -0,0 +1,71 @@
|
||||
---
|
||||
title: Version and Minimize localStorage Data
|
||||
impact: MEDIUM
|
||||
impactDescription: prevents schema conflicts, reduces storage size
|
||||
tags: client, localStorage, storage, versioning, data-minimization
|
||||
---
|
||||
|
||||
## Version and Minimize localStorage Data
|
||||
|
||||
Add version prefix to keys and store only needed fields. Prevents schema conflicts and accidental storage of sensitive data.
|
||||
|
||||
**Incorrect:**
|
||||
|
||||
```typescript
|
||||
// No version, stores everything, no error handling
|
||||
localStorage.setItem('userConfig', JSON.stringify(fullUserObject))
|
||||
const data = localStorage.getItem('userConfig')
|
||||
```
|
||||
|
||||
**Correct:**
|
||||
|
||||
```typescript
|
||||
const VERSION = 'v2'
|
||||
|
||||
function saveConfig(config: { theme: string; language: string }) {
|
||||
try {
|
||||
localStorage.setItem(`userConfig:${VERSION}`, JSON.stringify(config))
|
||||
} catch {
|
||||
// Throws in incognito/private browsing, quota exceeded, or disabled
|
||||
}
|
||||
}
|
||||
|
||||
function loadConfig() {
|
||||
try {
|
||||
const data = localStorage.getItem(`userConfig:${VERSION}`)
|
||||
return data ? JSON.parse(data) : null
|
||||
} catch {
|
||||
return null
|
||||
}
|
||||
}
|
||||
|
||||
// Migration from v1 to v2
|
||||
function migrate() {
|
||||
try {
|
||||
const v1 = localStorage.getItem('userConfig:v1')
|
||||
if (v1) {
|
||||
const old = JSON.parse(v1)
|
||||
saveConfig({ theme: old.darkMode ? 'dark' : 'light', language: old.lang })
|
||||
localStorage.removeItem('userConfig:v1')
|
||||
}
|
||||
} catch {}
|
||||
}
|
||||
```
|
||||
|
||||
**Store minimal fields from server responses:**
|
||||
|
||||
```typescript
|
||||
// User object has 20+ fields, only store what UI needs
|
||||
function cachePrefs(user: FullUser) {
|
||||
try {
|
||||
localStorage.setItem('prefs:v1', JSON.stringify({
|
||||
theme: user.preferences.theme,
|
||||
notifications: user.preferences.notifications
|
||||
}))
|
||||
} catch {}
|
||||
}
|
||||
```
|
||||
|
||||
**Always wrap in try-catch:** `getItem()` and `setItem()` throw in incognito/private browsing (Safari, Firefox), when quota exceeded, or when disabled.
|
||||
|
||||
**Benefits:** Schema evolution via versioning, reduced storage size, prevents storing tokens/PII/internal flags.
|
||||
@@ -0,0 +1,48 @@
|
||||
---
|
||||
title: Use Passive Event Listeners for Scrolling Performance
|
||||
impact: MEDIUM
|
||||
impactDescription: eliminates scroll delay caused by event listeners
|
||||
tags: client, event-listeners, scrolling, performance, touch, wheel
|
||||
---
|
||||
|
||||
## Use Passive Event Listeners for Scrolling Performance
|
||||
|
||||
Add `{ passive: true }` to touch and wheel event listeners to enable immediate scrolling. Browsers normally wait for listeners to finish to check if `preventDefault()` is called, causing scroll delay.
|
||||
|
||||
**Incorrect:**
|
||||
|
||||
```typescript
|
||||
useEffect(() => {
|
||||
const handleTouch = (e: TouchEvent) => console.log(e.touches[0].clientX)
|
||||
const handleWheel = (e: WheelEvent) => console.log(e.deltaY)
|
||||
|
||||
document.addEventListener('touchstart', handleTouch)
|
||||
document.addEventListener('wheel', handleWheel)
|
||||
|
||||
return () => {
|
||||
document.removeEventListener('touchstart', handleTouch)
|
||||
document.removeEventListener('wheel', handleWheel)
|
||||
}
|
||||
}, [])
|
||||
```
|
||||
|
||||
**Correct:**
|
||||
|
||||
```typescript
|
||||
useEffect(() => {
|
||||
const handleTouch = (e: TouchEvent) => console.log(e.touches[0].clientX)
|
||||
const handleWheel = (e: WheelEvent) => console.log(e.deltaY)
|
||||
|
||||
document.addEventListener('touchstart', handleTouch, { passive: true })
|
||||
document.addEventListener('wheel', handleWheel, { passive: true })
|
||||
|
||||
return () => {
|
||||
document.removeEventListener('touchstart', handleTouch)
|
||||
document.removeEventListener('wheel', handleWheel)
|
||||
}
|
||||
}, [])
|
||||
```
|
||||
|
||||
**Use passive when:** tracking/analytics, logging, any listener that doesn't call `preventDefault()`.
|
||||
|
||||
**Don't use passive when:** implementing custom swipe gestures, custom zoom controls, or any listener that needs `preventDefault()`.
|
||||
@@ -0,0 +1,56 @@
|
||||
---
|
||||
title: Use SWR for Automatic Deduplication
|
||||
impact: MEDIUM-HIGH
|
||||
impactDescription: automatic deduplication
|
||||
tags: client, swr, deduplication, data-fetching
|
||||
---
|
||||
|
||||
## Use SWR for Automatic Deduplication
|
||||
|
||||
SWR enables request deduplication, caching, and revalidation across component instances.
|
||||
|
||||
**Incorrect (no deduplication, each instance fetches):**
|
||||
|
||||
```tsx
|
||||
function UserList() {
|
||||
const [users, setUsers] = useState([])
|
||||
useEffect(() => {
|
||||
fetch('/api/users')
|
||||
.then(r => r.json())
|
||||
.then(setUsers)
|
||||
}, [])
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (multiple instances share one request):**
|
||||
|
||||
```tsx
|
||||
import useSWR from 'swr'
|
||||
|
||||
function UserList() {
|
||||
const { data: users } = useSWR('/api/users', fetcher)
|
||||
}
|
||||
```
|
||||
|
||||
**For immutable data:**
|
||||
|
||||
```tsx
|
||||
import { useImmutableSWR } from '@/lib/swr'
|
||||
|
||||
function StaticContent() {
|
||||
const { data } = useImmutableSWR('/api/config', fetcher)
|
||||
}
|
||||
```
|
||||
|
||||
**For mutations:**
|
||||
|
||||
```tsx
|
||||
import { useSWRMutation } from 'swr/mutation'
|
||||
|
||||
function UpdateButton() {
|
||||
const { trigger } = useSWRMutation('/api/user', updateUser)
|
||||
return <button onClick={() => trigger()}>Update</button>
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [https://swr.vercel.app](https://swr.vercel.app)
|
||||
@@ -0,0 +1,107 @@
|
||||
---
|
||||
title: Avoid Layout Thrashing
|
||||
impact: MEDIUM
|
||||
impactDescription: prevents forced synchronous layouts and reduces performance bottlenecks
|
||||
tags: javascript, dom, css, performance, reflow, layout-thrashing
|
||||
---
|
||||
|
||||
## Avoid Layout Thrashing
|
||||
|
||||
Avoid interleaving style writes with layout reads. When you read a layout property (like `offsetWidth`, `getBoundingClientRect()`, or `getComputedStyle()`) between style changes, the browser is forced to trigger a synchronous reflow.
|
||||
|
||||
**This is OK (browser batches style changes):**
|
||||
```typescript
|
||||
function updateElementStyles(element: HTMLElement) {
|
||||
// Each line invalidates style, but browser batches the recalculation
|
||||
element.style.width = '100px'
|
||||
element.style.height = '200px'
|
||||
element.style.backgroundColor = 'blue'
|
||||
element.style.border = '1px solid black'
|
||||
}
|
||||
```
|
||||
|
||||
**Incorrect (interleaved reads and writes force reflows):**
|
||||
```typescript
|
||||
function layoutThrashing(element: HTMLElement) {
|
||||
element.style.width = '100px'
|
||||
const width = element.offsetWidth // Forces reflow
|
||||
element.style.height = '200px'
|
||||
const height = element.offsetHeight // Forces another reflow
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (batch writes, then read once):**
|
||||
```typescript
|
||||
function updateElementStyles(element: HTMLElement) {
|
||||
// Batch all writes together
|
||||
element.style.width = '100px'
|
||||
element.style.height = '200px'
|
||||
element.style.backgroundColor = 'blue'
|
||||
element.style.border = '1px solid black'
|
||||
|
||||
// Read after all writes are done (single reflow)
|
||||
const { width, height } = element.getBoundingClientRect()
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (batch reads, then writes):**
|
||||
```typescript
|
||||
function avoidThrashing(element: HTMLElement) {
|
||||
// Read phase - all layout queries first
|
||||
const rect1 = element.getBoundingClientRect()
|
||||
const offsetWidth = element.offsetWidth
|
||||
const offsetHeight = element.offsetHeight
|
||||
|
||||
// Write phase - all style changes after
|
||||
element.style.width = '100px'
|
||||
element.style.height = '200px'
|
||||
}
|
||||
```
|
||||
|
||||
**Better: use CSS classes**
|
||||
```css
|
||||
.highlighted-box {
|
||||
width: 100px;
|
||||
height: 200px;
|
||||
background-color: blue;
|
||||
border: 1px solid black;
|
||||
}
|
||||
```
|
||||
```typescript
|
||||
function updateElementStyles(element: HTMLElement) {
|
||||
element.classList.add('highlighted-box')
|
||||
|
||||
const { width, height } = element.getBoundingClientRect()
|
||||
}
|
||||
```
|
||||
|
||||
**React example:**
|
||||
```tsx
|
||||
// Incorrect: interleaving style changes with layout queries
|
||||
function Box({ isHighlighted }: { isHighlighted: boolean }) {
|
||||
const ref = useRef<HTMLDivElement>(null)
|
||||
|
||||
useEffect(() => {
|
||||
if (ref.current && isHighlighted) {
|
||||
ref.current.style.width = '100px'
|
||||
const width = ref.current.offsetWidth // Forces layout
|
||||
ref.current.style.height = '200px'
|
||||
}
|
||||
}, [isHighlighted])
|
||||
|
||||
return <div ref={ref}>Content</div>
|
||||
}
|
||||
|
||||
// Correct: toggle class
|
||||
function Box({ isHighlighted }: { isHighlighted: boolean }) {
|
||||
return (
|
||||
<div className={isHighlighted ? 'highlighted-box' : ''}>
|
||||
Content
|
||||
</div>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
Prefer CSS classes over inline styles when possible. CSS files are cached by the browser, and classes provide better separation of concerns and are easier to maintain.
|
||||
|
||||
See [this gist](https://gist.github.com/paulirish/5d52fb081b3570c81e3a) and [CSS Triggers](https://csstriggers.com/) for more information on layout-forcing operations.
|
||||
@@ -0,0 +1,80 @@
|
||||
---
|
||||
title: Cache Repeated Function Calls
|
||||
impact: MEDIUM
|
||||
impactDescription: avoid redundant computation
|
||||
tags: javascript, cache, memoization, performance
|
||||
---
|
||||
|
||||
## Cache Repeated Function Calls
|
||||
|
||||
Use a module-level Map to cache function results when the same function is called repeatedly with the same inputs during render.
|
||||
|
||||
**Incorrect (redundant computation):**
|
||||
|
||||
```typescript
|
||||
function ProjectList({ projects }: { projects: Project[] }) {
|
||||
return (
|
||||
<div>
|
||||
{projects.map(project => {
|
||||
// slugify() called 100+ times for same project names
|
||||
const slug = slugify(project.name)
|
||||
|
||||
return <ProjectCard key={project.id} slug={slug} />
|
||||
})}
|
||||
</div>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (cached results):**
|
||||
|
||||
```typescript
|
||||
// Module-level cache
|
||||
const slugifyCache = new Map<string, string>()
|
||||
|
||||
function cachedSlugify(text: string): string {
|
||||
if (slugifyCache.has(text)) {
|
||||
return slugifyCache.get(text)!
|
||||
}
|
||||
const result = slugify(text)
|
||||
slugifyCache.set(text, result)
|
||||
return result
|
||||
}
|
||||
|
||||
function ProjectList({ projects }: { projects: Project[] }) {
|
||||
return (
|
||||
<div>
|
||||
{projects.map(project => {
|
||||
// Computed only once per unique project name
|
||||
const slug = cachedSlugify(project.name)
|
||||
|
||||
return <ProjectCard key={project.id} slug={slug} />
|
||||
})}
|
||||
</div>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Simpler pattern for single-value functions:**
|
||||
|
||||
```typescript
|
||||
let isLoggedInCache: boolean | null = null
|
||||
|
||||
function isLoggedIn(): boolean {
|
||||
if (isLoggedInCache !== null) {
|
||||
return isLoggedInCache
|
||||
}
|
||||
|
||||
isLoggedInCache = document.cookie.includes('auth=')
|
||||
return isLoggedInCache
|
||||
}
|
||||
|
||||
// Clear cache when auth changes
|
||||
function onAuthChange() {
|
||||
isLoggedInCache = null
|
||||
}
|
||||
```
|
||||
|
||||
Use a Map (not a hook) so it works everywhere: utilities, event handlers, not just React components.
|
||||
|
||||
Reference: [How we made the Vercel Dashboard twice as fast](https://vercel.com/blog/how-we-made-the-vercel-dashboard-twice-as-fast)
|
||||
@@ -0,0 +1,28 @@
|
||||
---
|
||||
title: Cache Property Access in Loops
|
||||
impact: LOW-MEDIUM
|
||||
impactDescription: reduces lookups
|
||||
tags: javascript, loops, optimization, caching
|
||||
---
|
||||
|
||||
## Cache Property Access in Loops
|
||||
|
||||
Cache object property lookups in hot paths.
|
||||
|
||||
**Incorrect (3 lookups × N iterations):**
|
||||
|
||||
```typescript
|
||||
for (let i = 0; i < arr.length; i++) {
|
||||
process(obj.config.settings.value)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (1 lookup total):**
|
||||
|
||||
```typescript
|
||||
const value = obj.config.settings.value
|
||||
const len = arr.length
|
||||
for (let i = 0; i < len; i++) {
|
||||
process(value)
|
||||
}
|
||||
```
|
||||
@@ -0,0 +1,70 @@
|
||||
---
|
||||
title: Cache Storage API Calls
|
||||
impact: LOW-MEDIUM
|
||||
impactDescription: reduces expensive I/O
|
||||
tags: javascript, localStorage, storage, caching, performance
|
||||
---
|
||||
|
||||
## Cache Storage API Calls
|
||||
|
||||
`localStorage`, `sessionStorage`, and `document.cookie` are synchronous and expensive. Cache reads in memory.
|
||||
|
||||
**Incorrect (reads storage on every call):**
|
||||
|
||||
```typescript
|
||||
function getTheme() {
|
||||
return localStorage.getItem('theme') ?? 'light'
|
||||
}
|
||||
// Called 10 times = 10 storage reads
|
||||
```
|
||||
|
||||
**Correct (Map cache):**
|
||||
|
||||
```typescript
|
||||
const storageCache = new Map<string, string | null>()
|
||||
|
||||
function getLocalStorage(key: string) {
|
||||
if (!storageCache.has(key)) {
|
||||
storageCache.set(key, localStorage.getItem(key))
|
||||
}
|
||||
return storageCache.get(key)
|
||||
}
|
||||
|
||||
function setLocalStorage(key: string, value: string) {
|
||||
localStorage.setItem(key, value)
|
||||
storageCache.set(key, value) // keep cache in sync
|
||||
}
|
||||
```
|
||||
|
||||
Use a Map (not a hook) so it works everywhere: utilities, event handlers, not just React components.
|
||||
|
||||
**Cookie caching:**
|
||||
|
||||
```typescript
|
||||
let cookieCache: Record<string, string> | null = null
|
||||
|
||||
function getCookie(name: string) {
|
||||
if (!cookieCache) {
|
||||
cookieCache = Object.fromEntries(
|
||||
document.cookie.split('; ').map(c => c.split('='))
|
||||
)
|
||||
}
|
||||
return cookieCache[name]
|
||||
}
|
||||
```
|
||||
|
||||
**Important (invalidate on external changes):**
|
||||
|
||||
If storage can change externally (another tab, server-set cookies), invalidate cache:
|
||||
|
||||
```typescript
|
||||
window.addEventListener('storage', (e) => {
|
||||
if (e.key) storageCache.delete(e.key)
|
||||
})
|
||||
|
||||
document.addEventListener('visibilitychange', () => {
|
||||
if (document.visibilityState === 'visible') {
|
||||
storageCache.clear()
|
||||
}
|
||||
})
|
||||
```
|
||||
@@ -0,0 +1,32 @@
|
||||
---
|
||||
title: Combine Multiple Array Iterations
|
||||
impact: LOW-MEDIUM
|
||||
impactDescription: reduces iterations
|
||||
tags: javascript, arrays, loops, performance
|
||||
---
|
||||
|
||||
## Combine Multiple Array Iterations
|
||||
|
||||
Multiple `.filter()` or `.map()` calls iterate the array multiple times. Combine into one loop.
|
||||
|
||||
**Incorrect (3 iterations):**
|
||||
|
||||
```typescript
|
||||
const admins = users.filter(u => u.isAdmin)
|
||||
const testers = users.filter(u => u.isTester)
|
||||
const inactive = users.filter(u => !u.isActive)
|
||||
```
|
||||
|
||||
**Correct (1 iteration):**
|
||||
|
||||
```typescript
|
||||
const admins: User[] = []
|
||||
const testers: User[] = []
|
||||
const inactive: User[] = []
|
||||
|
||||
for (const user of users) {
|
||||
if (user.isAdmin) admins.push(user)
|
||||
if (user.isTester) testers.push(user)
|
||||
if (!user.isActive) inactive.push(user)
|
||||
}
|
||||
```
|
||||
@@ -0,0 +1,50 @@
|
||||
---
|
||||
title: Early Return from Functions
|
||||
impact: LOW-MEDIUM
|
||||
impactDescription: avoids unnecessary computation
|
||||
tags: javascript, functions, optimization, early-return
|
||||
---
|
||||
|
||||
## Early Return from Functions
|
||||
|
||||
Return early when result is determined to skip unnecessary processing.
|
||||
|
||||
**Incorrect (processes all items even after finding answer):**
|
||||
|
||||
```typescript
|
||||
function validateUsers(users: User[]) {
|
||||
let hasError = false
|
||||
let errorMessage = ''
|
||||
|
||||
for (const user of users) {
|
||||
if (!user.email) {
|
||||
hasError = true
|
||||
errorMessage = 'Email required'
|
||||
}
|
||||
if (!user.name) {
|
||||
hasError = true
|
||||
errorMessage = 'Name required'
|
||||
}
|
||||
// Continues checking all users even after error found
|
||||
}
|
||||
|
||||
return hasError ? { valid: false, error: errorMessage } : { valid: true }
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (returns immediately on first error):**
|
||||
|
||||
```typescript
|
||||
function validateUsers(users: User[]) {
|
||||
for (const user of users) {
|
||||
if (!user.email) {
|
||||
return { valid: false, error: 'Email required' }
|
||||
}
|
||||
if (!user.name) {
|
||||
return { valid: false, error: 'Name required' }
|
||||
}
|
||||
}
|
||||
|
||||
return { valid: true }
|
||||
}
|
||||
```
|
||||
@@ -0,0 +1,60 @@
|
||||
---
|
||||
title: Use flatMap to Map and Filter in One Pass
|
||||
impact: LOW-MEDIUM
|
||||
impactDescription: eliminates intermediate array
|
||||
tags: javascript, arrays, flatMap, filter, performance
|
||||
---
|
||||
|
||||
## Use flatMap to Map and Filter in One Pass
|
||||
|
||||
**Impact: LOW-MEDIUM (eliminates intermediate array)**
|
||||
|
||||
Chaining `.map().filter(Boolean)` creates an intermediate array and iterates twice. Use `.flatMap()` to transform and filter in a single pass.
|
||||
|
||||
**Incorrect (2 iterations, intermediate array):**
|
||||
|
||||
```typescript
|
||||
const userNames = users
|
||||
.map(user => user.isActive ? user.name : null)
|
||||
.filter(Boolean)
|
||||
```
|
||||
|
||||
**Correct (1 iteration, no intermediate array):**
|
||||
|
||||
```typescript
|
||||
const userNames = users.flatMap(user =>
|
||||
user.isActive ? [user.name] : []
|
||||
)
|
||||
```
|
||||
|
||||
**More examples:**
|
||||
|
||||
```typescript
|
||||
// Extract valid emails from responses
|
||||
// Before
|
||||
const emails = responses
|
||||
.map(r => r.success ? r.data.email : null)
|
||||
.filter(Boolean)
|
||||
|
||||
// After
|
||||
const emails = responses.flatMap(r =>
|
||||
r.success ? [r.data.email] : []
|
||||
)
|
||||
|
||||
// Parse and filter valid numbers
|
||||
// Before
|
||||
const numbers = strings
|
||||
.map(s => parseInt(s, 10))
|
||||
.filter(n => !isNaN(n))
|
||||
|
||||
// After
|
||||
const numbers = strings.flatMap(s => {
|
||||
const n = parseInt(s, 10)
|
||||
return isNaN(n) ? [] : [n]
|
||||
})
|
||||
```
|
||||
|
||||
**When to use:**
|
||||
- Transforming items while filtering some out
|
||||
- Conditional mapping where some inputs produce no output
|
||||
- Parsing/validating where invalid inputs should be skipped
|
||||
@@ -0,0 +1,45 @@
|
||||
---
|
||||
title: Hoist RegExp Creation
|
||||
impact: LOW-MEDIUM
|
||||
impactDescription: avoids recreation
|
||||
tags: javascript, regexp, optimization, memoization
|
||||
---
|
||||
|
||||
## Hoist RegExp Creation
|
||||
|
||||
Don't create RegExp inside render. Hoist to module scope or memoize with `useMemo()`.
|
||||
|
||||
**Incorrect (new RegExp every render):**
|
||||
|
||||
```tsx
|
||||
function Highlighter({ text, query }: Props) {
|
||||
const regex = new RegExp(`(${query})`, 'gi')
|
||||
const parts = text.split(regex)
|
||||
return <>{parts.map((part, i) => ...)}</>
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (memoize or hoist):**
|
||||
|
||||
```tsx
|
||||
const EMAIL_REGEX = /^[^\s@]+@[^\s@]+\.[^\s@]+$/
|
||||
|
||||
function Highlighter({ text, query }: Props) {
|
||||
const regex = useMemo(
|
||||
() => new RegExp(`(${escapeRegex(query)})`, 'gi'),
|
||||
[query]
|
||||
)
|
||||
const parts = text.split(regex)
|
||||
return <>{parts.map((part, i) => ...)}</>
|
||||
}
|
||||
```
|
||||
|
||||
**Warning (global regex has mutable state):**
|
||||
|
||||
Global regex (`/g`) has mutable `lastIndex` state:
|
||||
|
||||
```typescript
|
||||
const regex = /foo/g
|
||||
regex.test('foo') // true, lastIndex = 3
|
||||
regex.test('foo') // false, lastIndex = 0
|
||||
```
|
||||
@@ -0,0 +1,37 @@
|
||||
---
|
||||
title: Build Index Maps for Repeated Lookups
|
||||
impact: LOW-MEDIUM
|
||||
impactDescription: 1M ops to 2K ops
|
||||
tags: javascript, map, indexing, optimization, performance
|
||||
---
|
||||
|
||||
## Build Index Maps for Repeated Lookups
|
||||
|
||||
Multiple `.find()` calls by the same key should use a Map.
|
||||
|
||||
**Incorrect (O(n) per lookup):**
|
||||
|
||||
```typescript
|
||||
function processOrders(orders: Order[], users: User[]) {
|
||||
return orders.map(order => ({
|
||||
...order,
|
||||
user: users.find(u => u.id === order.userId)
|
||||
}))
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (O(1) per lookup):**
|
||||
|
||||
```typescript
|
||||
function processOrders(orders: Order[], users: User[]) {
|
||||
const userById = new Map(users.map(u => [u.id, u]))
|
||||
|
||||
return orders.map(order => ({
|
||||
...order,
|
||||
user: userById.get(order.userId)
|
||||
}))
|
||||
}
|
||||
```
|
||||
|
||||
Build map once (O(n)), then all lookups are O(1).
|
||||
For 1000 orders × 1000 users: 1M ops → 2K ops.
|
||||
@@ -0,0 +1,49 @@
|
||||
---
|
||||
title: Early Length Check for Array Comparisons
|
||||
impact: MEDIUM-HIGH
|
||||
impactDescription: avoids expensive operations when lengths differ
|
||||
tags: javascript, arrays, performance, optimization, comparison
|
||||
---
|
||||
|
||||
## Early Length Check for Array Comparisons
|
||||
|
||||
When comparing arrays with expensive operations (sorting, deep equality, serialization), check lengths first. If lengths differ, the arrays cannot be equal.
|
||||
|
||||
In real-world applications, this optimization is especially valuable when the comparison runs in hot paths (event handlers, render loops).
|
||||
|
||||
**Incorrect (always runs expensive comparison):**
|
||||
|
||||
```typescript
|
||||
function hasChanges(current: string[], original: string[]) {
|
||||
// Always sorts and joins, even when lengths differ
|
||||
return current.sort().join() !== original.sort().join()
|
||||
}
|
||||
```
|
||||
|
||||
Two O(n log n) sorts run even when `current.length` is 5 and `original.length` is 100. There is also overhead of joining the arrays and comparing the strings.
|
||||
|
||||
**Correct (O(1) length check first):**
|
||||
|
||||
```typescript
|
||||
function hasChanges(current: string[], original: string[]) {
|
||||
// Early return if lengths differ
|
||||
if (current.length !== original.length) {
|
||||
return true
|
||||
}
|
||||
// Only sort when lengths match
|
||||
const currentSorted = current.toSorted()
|
||||
const originalSorted = original.toSorted()
|
||||
for (let i = 0; i < currentSorted.length; i++) {
|
||||
if (currentSorted[i] !== originalSorted[i]) {
|
||||
return true
|
||||
}
|
||||
}
|
||||
return false
|
||||
}
|
||||
```
|
||||
|
||||
This new approach is more efficient because:
|
||||
- It avoids the overhead of sorting and joining the arrays when lengths differ
|
||||
- It avoids consuming memory for the joined strings (especially important for large arrays)
|
||||
- It avoids mutating the original arrays
|
||||
- It returns early when a difference is found
|
||||
@@ -0,0 +1,82 @@
|
||||
---
|
||||
title: Use Loop for Min/Max Instead of Sort
|
||||
impact: LOW
|
||||
impactDescription: O(n) instead of O(n log n)
|
||||
tags: javascript, arrays, performance, sorting, algorithms
|
||||
---
|
||||
|
||||
## Use Loop for Min/Max Instead of Sort
|
||||
|
||||
Finding the smallest or largest element only requires a single pass through the array. Sorting is wasteful and slower.
|
||||
|
||||
**Incorrect (O(n log n) - sort to find latest):**
|
||||
|
||||
```typescript
|
||||
interface Project {
|
||||
id: string
|
||||
name: string
|
||||
updatedAt: number
|
||||
}
|
||||
|
||||
function getLatestProject(projects: Project[]) {
|
||||
const sorted = [...projects].sort((a, b) => b.updatedAt - a.updatedAt)
|
||||
return sorted[0]
|
||||
}
|
||||
```
|
||||
|
||||
Sorts the entire array just to find the maximum value.
|
||||
|
||||
**Incorrect (O(n log n) - sort for oldest and newest):**
|
||||
|
||||
```typescript
|
||||
function getOldestAndNewest(projects: Project[]) {
|
||||
const sorted = [...projects].sort((a, b) => a.updatedAt - b.updatedAt)
|
||||
return { oldest: sorted[0], newest: sorted[sorted.length - 1] }
|
||||
}
|
||||
```
|
||||
|
||||
Still sorts unnecessarily when only min/max are needed.
|
||||
|
||||
**Correct (O(n) - single loop):**
|
||||
|
||||
```typescript
|
||||
function getLatestProject(projects: Project[]) {
|
||||
if (projects.length === 0) return null
|
||||
|
||||
let latest = projects[0]
|
||||
|
||||
for (let i = 1; i < projects.length; i++) {
|
||||
if (projects[i].updatedAt > latest.updatedAt) {
|
||||
latest = projects[i]
|
||||
}
|
||||
}
|
||||
|
||||
return latest
|
||||
}
|
||||
|
||||
function getOldestAndNewest(projects: Project[]) {
|
||||
if (projects.length === 0) return { oldest: null, newest: null }
|
||||
|
||||
let oldest = projects[0]
|
||||
let newest = projects[0]
|
||||
|
||||
for (let i = 1; i < projects.length; i++) {
|
||||
if (projects[i].updatedAt < oldest.updatedAt) oldest = projects[i]
|
||||
if (projects[i].updatedAt > newest.updatedAt) newest = projects[i]
|
||||
}
|
||||
|
||||
return { oldest, newest }
|
||||
}
|
||||
```
|
||||
|
||||
Single pass through the array, no copying, no sorting.
|
||||
|
||||
**Alternative (Math.min/Math.max for small arrays):**
|
||||
|
||||
```typescript
|
||||
const numbers = [5, 2, 8, 1, 9]
|
||||
const min = Math.min(...numbers)
|
||||
const max = Math.max(...numbers)
|
||||
```
|
||||
|
||||
This works for small arrays, but can be slower or just throw an error for very large arrays due to spread operator limitations. Maximal array length is approximately 124000 in Chrome 143 and 638000 in Safari 18; exact numbers may vary - see [the fiddle](https://jsfiddle.net/qw1jabsx/4/). Use the loop approach for reliability.
|
||||
@@ -0,0 +1,105 @@
|
||||
---
|
||||
title: Defer Non-Critical Work with requestIdleCallback
|
||||
impact: MEDIUM
|
||||
impactDescription: keeps UI responsive during background tasks
|
||||
tags: javascript, performance, idle, scheduling, analytics
|
||||
---
|
||||
|
||||
## Defer Non-Critical Work with requestIdleCallback
|
||||
|
||||
**Impact: MEDIUM (keeps UI responsive during background tasks)**
|
||||
|
||||
Use `requestIdleCallback()` to schedule non-critical work during browser idle periods. This keeps the main thread free for user interactions and animations, reducing jank and improving perceived performance.
|
||||
|
||||
**Incorrect (blocks main thread during user interaction):**
|
||||
|
||||
```typescript
|
||||
function handleSearch(query: string) {
|
||||
const results = searchItems(query)
|
||||
setResults(results)
|
||||
|
||||
// These block the main thread immediately
|
||||
analytics.track('search', { query })
|
||||
saveToRecentSearches(query)
|
||||
prefetchTopResults(results.slice(0, 3))
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (defers non-critical work to idle time):**
|
||||
|
||||
```typescript
|
||||
function handleSearch(query: string) {
|
||||
const results = searchItems(query)
|
||||
setResults(results)
|
||||
|
||||
// Defer non-critical work to idle periods
|
||||
requestIdleCallback(() => {
|
||||
analytics.track('search', { query })
|
||||
})
|
||||
|
||||
requestIdleCallback(() => {
|
||||
saveToRecentSearches(query)
|
||||
})
|
||||
|
||||
requestIdleCallback(() => {
|
||||
prefetchTopResults(results.slice(0, 3))
|
||||
})
|
||||
}
|
||||
```
|
||||
|
||||
**With timeout for required work:**
|
||||
|
||||
```typescript
|
||||
// Ensure analytics fires within 2 seconds even if browser stays busy
|
||||
requestIdleCallback(
|
||||
() => analytics.track('page_view', { path: location.pathname }),
|
||||
{ timeout: 2000 }
|
||||
)
|
||||
```
|
||||
|
||||
**Chunking large tasks:**
|
||||
|
||||
```typescript
|
||||
function processLargeDataset(items: Item[]) {
|
||||
let index = 0
|
||||
|
||||
function processChunk(deadline: IdleDeadline) {
|
||||
// Process items while we have idle time (aim for <50ms chunks)
|
||||
while (index < items.length && deadline.timeRemaining() > 0) {
|
||||
processItem(items[index])
|
||||
index++
|
||||
}
|
||||
|
||||
// Schedule next chunk if more items remain
|
||||
if (index < items.length) {
|
||||
requestIdleCallback(processChunk)
|
||||
}
|
||||
}
|
||||
|
||||
requestIdleCallback(processChunk)
|
||||
}
|
||||
```
|
||||
|
||||
**With fallback for unsupported browsers:**
|
||||
|
||||
```typescript
|
||||
const scheduleIdleWork = window.requestIdleCallback ?? ((cb: () => void) => setTimeout(cb, 1))
|
||||
|
||||
scheduleIdleWork(() => {
|
||||
// Non-critical work
|
||||
})
|
||||
```
|
||||
|
||||
**When to use:**
|
||||
|
||||
- Analytics and telemetry
|
||||
- Saving state to localStorage/IndexedDB
|
||||
- Prefetching resources for likely next actions
|
||||
- Processing non-urgent data transformations
|
||||
- Lazy initialization of non-critical features
|
||||
|
||||
**When NOT to use:**
|
||||
|
||||
- User-initiated actions that need immediate feedback
|
||||
- Rendering updates the user is waiting for
|
||||
- Time-sensitive operations
|
||||
@@ -0,0 +1,24 @@
|
||||
---
|
||||
title: Use Set/Map for O(1) Lookups
|
||||
impact: LOW-MEDIUM
|
||||
impactDescription: O(n) to O(1)
|
||||
tags: javascript, set, map, data-structures, performance
|
||||
---
|
||||
|
||||
## Use Set/Map for O(1) Lookups
|
||||
|
||||
Convert arrays to Set/Map for repeated membership checks.
|
||||
|
||||
**Incorrect (O(n) per check):**
|
||||
|
||||
```typescript
|
||||
const allowedIds = ['a', 'b', 'c', ...]
|
||||
items.filter(item => allowedIds.includes(item.id))
|
||||
```
|
||||
|
||||
**Correct (O(1) per check):**
|
||||
|
||||
```typescript
|
||||
const allowedIds = new Set(['a', 'b', 'c', ...])
|
||||
items.filter(item => allowedIds.has(item.id))
|
||||
```
|
||||
@@ -0,0 +1,57 @@
|
||||
---
|
||||
title: Use toSorted() Instead of sort() for Immutability
|
||||
impact: MEDIUM-HIGH
|
||||
impactDescription: prevents mutation bugs in React state
|
||||
tags: javascript, arrays, immutability, react, state, mutation
|
||||
---
|
||||
|
||||
## Use toSorted() Instead of sort() for Immutability
|
||||
|
||||
`.sort()` mutates the array in place, which can cause bugs with React state and props. Use `.toSorted()` to create a new sorted array without mutation.
|
||||
|
||||
**Incorrect (mutates original array):**
|
||||
|
||||
```typescript
|
||||
function UserList({ users }: { users: User[] }) {
|
||||
// Mutates the users prop array!
|
||||
const sorted = useMemo(
|
||||
() => users.sort((a, b) => a.name.localeCompare(b.name)),
|
||||
[users]
|
||||
)
|
||||
return <div>{sorted.map(renderUser)}</div>
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (creates new array):**
|
||||
|
||||
```typescript
|
||||
function UserList({ users }: { users: User[] }) {
|
||||
// Creates new sorted array, original unchanged
|
||||
const sorted = useMemo(
|
||||
() => users.toSorted((a, b) => a.name.localeCompare(b.name)),
|
||||
[users]
|
||||
)
|
||||
return <div>{sorted.map(renderUser)}</div>
|
||||
}
|
||||
```
|
||||
|
||||
**Why this matters in React:**
|
||||
|
||||
1. Props/state mutations break React's immutability model - React expects props and state to be treated as read-only
|
||||
2. Causes stale closure bugs - Mutating arrays inside closures (callbacks, effects) can lead to unexpected behavior
|
||||
|
||||
**Browser support (fallback for older browsers):**
|
||||
|
||||
`.toSorted()` is available in all modern browsers (Chrome 110+, Safari 16+, Firefox 115+, Node.js 20+). For older environments, use spread operator:
|
||||
|
||||
```typescript
|
||||
// Fallback for older browsers
|
||||
const sorted = [...items].sort((a, b) => a.value - b.value)
|
||||
```
|
||||
|
||||
**Other immutable array methods:**
|
||||
|
||||
- `.toSorted()` - immutable sort
|
||||
- `.toReversed()` - immutable reverse
|
||||
- `.toSpliced()` - immutable splice
|
||||
- `.with()` - immutable element replacement
|
||||
@@ -0,0 +1,26 @@
|
||||
---
|
||||
title: Use Activity Component for Show/Hide
|
||||
impact: MEDIUM
|
||||
impactDescription: preserves state/DOM
|
||||
tags: rendering, activity, visibility, state-preservation
|
||||
---
|
||||
|
||||
## Use Activity Component for Show/Hide
|
||||
|
||||
Use React's `<Activity>` to preserve state/DOM for expensive components that frequently toggle visibility.
|
||||
|
||||
**Usage:**
|
||||
|
||||
```tsx
|
||||
import { Activity } from 'react'
|
||||
|
||||
function Dropdown({ isOpen }: Props) {
|
||||
return (
|
||||
<Activity mode={isOpen ? 'visible' : 'hidden'}>
|
||||
<ExpensiveMenu />
|
||||
</Activity>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
Avoids expensive re-renders and state loss.
|
||||
@@ -0,0 +1,47 @@
|
||||
---
|
||||
title: Animate SVG Wrapper Instead of SVG Element
|
||||
impact: LOW
|
||||
impactDescription: enables hardware acceleration
|
||||
tags: rendering, svg, css, animation, performance
|
||||
---
|
||||
|
||||
## Animate SVG Wrapper Instead of SVG Element
|
||||
|
||||
Many browsers don't have hardware acceleration for CSS3 animations on SVG elements. Wrap SVG in a `<div>` and animate the wrapper instead.
|
||||
|
||||
**Incorrect (animating SVG directly - no hardware acceleration):**
|
||||
|
||||
```tsx
|
||||
function LoadingSpinner() {
|
||||
return (
|
||||
<svg
|
||||
className="animate-spin"
|
||||
width="24"
|
||||
height="24"
|
||||
viewBox="0 0 24 24"
|
||||
>
|
||||
<circle cx="12" cy="12" r="10" stroke="currentColor" />
|
||||
</svg>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (animating wrapper div - hardware accelerated):**
|
||||
|
||||
```tsx
|
||||
function LoadingSpinner() {
|
||||
return (
|
||||
<div className="animate-spin">
|
||||
<svg
|
||||
width="24"
|
||||
height="24"
|
||||
viewBox="0 0 24 24"
|
||||
>
|
||||
<circle cx="12" cy="12" r="10" stroke="currentColor" />
|
||||
</svg>
|
||||
</div>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
This applies to all CSS transforms and transitions (`transform`, `opacity`, `translate`, `scale`, `rotate`). The wrapper div allows browsers to use GPU acceleration for smoother animations.
|
||||
@@ -0,0 +1,40 @@
|
||||
---
|
||||
title: Use Explicit Conditional Rendering
|
||||
impact: LOW
|
||||
impactDescription: prevents rendering 0 or NaN
|
||||
tags: rendering, conditional, jsx, falsy-values
|
||||
---
|
||||
|
||||
## Use Explicit Conditional Rendering
|
||||
|
||||
Use explicit ternary operators (`? :`) instead of `&&` for conditional rendering when the condition can be `0`, `NaN`, or other falsy values that render.
|
||||
|
||||
**Incorrect (renders "0" when count is 0):**
|
||||
|
||||
```tsx
|
||||
function Badge({ count }: { count: number }) {
|
||||
return (
|
||||
<div>
|
||||
{count && <span className="badge">{count}</span>}
|
||||
</div>
|
||||
)
|
||||
}
|
||||
|
||||
// When count = 0, renders: <div>0</div>
|
||||
// When count = 5, renders: <div><span class="badge">5</span></div>
|
||||
```
|
||||
|
||||
**Correct (renders nothing when count is 0):**
|
||||
|
||||
```tsx
|
||||
function Badge({ count }: { count: number }) {
|
||||
return (
|
||||
<div>
|
||||
{count > 0 ? <span className="badge">{count}</span> : null}
|
||||
</div>
|
||||
)
|
||||
}
|
||||
|
||||
// When count = 0, renders: <div></div>
|
||||
// When count = 5, renders: <div><span class="badge">5</span></div>
|
||||
```
|
||||
@@ -0,0 +1,38 @@
|
||||
---
|
||||
title: CSS content-visibility for Long Lists
|
||||
impact: HIGH
|
||||
impactDescription: faster initial render
|
||||
tags: rendering, css, content-visibility, long-lists
|
||||
---
|
||||
|
||||
## CSS content-visibility for Long Lists
|
||||
|
||||
Apply `content-visibility: auto` to defer off-screen rendering.
|
||||
|
||||
**CSS:**
|
||||
|
||||
```css
|
||||
.message-item {
|
||||
content-visibility: auto;
|
||||
contain-intrinsic-size: 0 80px;
|
||||
}
|
||||
```
|
||||
|
||||
**Example:**
|
||||
|
||||
```tsx
|
||||
function MessageList({ messages }: { messages: Message[] }) {
|
||||
return (
|
||||
<div className="overflow-y-auto h-screen">
|
||||
{messages.map(msg => (
|
||||
<div key={msg.id} className="message-item">
|
||||
<Avatar user={msg.author} />
|
||||
<div>{msg.content}</div>
|
||||
</div>
|
||||
))}
|
||||
</div>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
For 1000 messages, browser skips layout/paint for ~990 off-screen items (10× faster initial render).
|
||||
@@ -0,0 +1,46 @@
|
||||
---
|
||||
title: Hoist Static JSX Elements
|
||||
impact: LOW
|
||||
impactDescription: avoids re-creation
|
||||
tags: rendering, jsx, static, optimization
|
||||
---
|
||||
|
||||
## Hoist Static JSX Elements
|
||||
|
||||
Extract static JSX outside components to avoid re-creation.
|
||||
|
||||
**Incorrect (recreates element every render):**
|
||||
|
||||
```tsx
|
||||
function LoadingSkeleton() {
|
||||
return <div className="animate-pulse h-20 bg-gray-200" />
|
||||
}
|
||||
|
||||
function Container() {
|
||||
return (
|
||||
<div>
|
||||
{loading && <LoadingSkeleton />}
|
||||
</div>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (reuses same element):**
|
||||
|
||||
```tsx
|
||||
const loadingSkeleton = (
|
||||
<div className="animate-pulse h-20 bg-gray-200" />
|
||||
)
|
||||
|
||||
function Container() {
|
||||
return (
|
||||
<div>
|
||||
{loading && loadingSkeleton}
|
||||
</div>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
This is especially helpful for large and static SVG nodes, which can be expensive to recreate on every render.
|
||||
|
||||
**Note:** If your project has [React Compiler](https://react.dev/learn/react-compiler) enabled, the compiler automatically hoists static JSX elements and optimizes component re-renders, making manual hoisting unnecessary.
|
||||
@@ -0,0 +1,82 @@
|
||||
---
|
||||
title: Prevent Hydration Mismatch Without Flickering
|
||||
impact: MEDIUM
|
||||
impactDescription: avoids visual flicker and hydration errors
|
||||
tags: rendering, ssr, hydration, localStorage, flicker
|
||||
---
|
||||
|
||||
## Prevent Hydration Mismatch Without Flickering
|
||||
|
||||
When rendering content that depends on client-side storage (localStorage, cookies), avoid both SSR breakage and post-hydration flickering by injecting a synchronous script that updates the DOM before React hydrates.
|
||||
|
||||
**Incorrect (breaks SSR):**
|
||||
|
||||
```tsx
|
||||
function ThemeWrapper({ children }: { children: ReactNode }) {
|
||||
// localStorage is not available on server - throws error
|
||||
const theme = localStorage.getItem('theme') || 'light'
|
||||
|
||||
return (
|
||||
<div className={theme}>
|
||||
{children}
|
||||
</div>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
Server-side rendering will fail because `localStorage` is undefined.
|
||||
|
||||
**Incorrect (visual flickering):**
|
||||
|
||||
```tsx
|
||||
function ThemeWrapper({ children }: { children: ReactNode }) {
|
||||
const [theme, setTheme] = useState('light')
|
||||
|
||||
useEffect(() => {
|
||||
// Runs after hydration - causes visible flash
|
||||
const stored = localStorage.getItem('theme')
|
||||
if (stored) {
|
||||
setTheme(stored)
|
||||
}
|
||||
}, [])
|
||||
|
||||
return (
|
||||
<div className={theme}>
|
||||
{children}
|
||||
</div>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
Component first renders with default value (`light`), then updates after hydration, causing a visible flash of incorrect content.
|
||||
|
||||
**Correct (no flicker, no hydration mismatch):**
|
||||
|
||||
```tsx
|
||||
function ThemeWrapper({ children }: { children: ReactNode }) {
|
||||
return (
|
||||
<>
|
||||
<div id="theme-wrapper">
|
||||
{children}
|
||||
</div>
|
||||
<script
|
||||
dangerouslySetInnerHTML={{
|
||||
__html: `
|
||||
(function() {
|
||||
try {
|
||||
var theme = localStorage.getItem('theme') || 'light';
|
||||
var el = document.getElementById('theme-wrapper');
|
||||
if (el) el.className = theme;
|
||||
} catch (e) {}
|
||||
})();
|
||||
`,
|
||||
}}
|
||||
/>
|
||||
</>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
The inline script executes synchronously before showing the element, ensuring the DOM already has the correct value. No flickering, no hydration mismatch.
|
||||
|
||||
This pattern is especially useful for theme toggles, user preferences, authentication states, and any client-only data that should render immediately without flashing default values.
|
||||
+30
@@ -0,0 +1,30 @@
|
||||
---
|
||||
title: Suppress Expected Hydration Mismatches
|
||||
impact: LOW-MEDIUM
|
||||
impactDescription: avoids noisy hydration warnings for known differences
|
||||
tags: rendering, hydration, ssr, nextjs
|
||||
---
|
||||
|
||||
## Suppress Expected Hydration Mismatches
|
||||
|
||||
In SSR frameworks (e.g., Next.js), some values are intentionally different on server vs client (random IDs, dates, locale/timezone formatting). For these *expected* mismatches, wrap the dynamic text in an element with `suppressHydrationWarning` to prevent noisy warnings. Do not use this to hide real bugs. Don’t overuse it.
|
||||
|
||||
**Incorrect (known mismatch warnings):**
|
||||
|
||||
```tsx
|
||||
function Timestamp() {
|
||||
return <span>{new Date().toLocaleString()}</span>
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (suppress expected mismatch only):**
|
||||
|
||||
```tsx
|
||||
function Timestamp() {
|
||||
return (
|
||||
<span suppressHydrationWarning>
|
||||
{new Date().toLocaleString()}
|
||||
</span>
|
||||
)
|
||||
}
|
||||
```
|
||||
@@ -0,0 +1,85 @@
|
||||
---
|
||||
title: Use React DOM Resource Hints
|
||||
impact: HIGH
|
||||
impactDescription: reduces load time for critical resources
|
||||
tags: rendering, preload, preconnect, prefetch, resource-hints
|
||||
---
|
||||
|
||||
## Use React DOM Resource Hints
|
||||
|
||||
**Impact: HIGH (reduces load time for critical resources)**
|
||||
|
||||
React DOM provides APIs to hint the browser about resources it will need. These are especially useful in server components to start loading resources before the client even receives the HTML.
|
||||
|
||||
- **`prefetchDNS(href)`**: Resolve DNS for a domain you expect to connect to
|
||||
- **`preconnect(href)`**: Establish connection (DNS + TCP + TLS) to a server
|
||||
- **`preload(href, options)`**: Fetch a resource (stylesheet, font, script, image) you'll use soon
|
||||
- **`preloadModule(href)`**: Fetch an ES module you'll use soon
|
||||
- **`preinit(href, options)`**: Fetch and evaluate a stylesheet or script
|
||||
- **`preinitModule(href)`**: Fetch and evaluate an ES module
|
||||
|
||||
**Example (preconnect to third-party APIs):**
|
||||
|
||||
```tsx
|
||||
import { preconnect, prefetchDNS } from 'react-dom'
|
||||
|
||||
export default function App() {
|
||||
prefetchDNS('https://analytics.example.com')
|
||||
preconnect('https://api.example.com')
|
||||
|
||||
return <main>{/* content */}</main>
|
||||
}
|
||||
```
|
||||
|
||||
**Example (preload critical fonts and styles):**
|
||||
|
||||
```tsx
|
||||
import { preload, preinit } from 'react-dom'
|
||||
|
||||
export default function RootLayout({ children }) {
|
||||
// Preload font file
|
||||
preload('/fonts/inter.woff2', { as: 'font', type: 'font/woff2', crossOrigin: 'anonymous' })
|
||||
|
||||
// Fetch and apply critical stylesheet immediately
|
||||
preinit('/styles/critical.css', { as: 'style' })
|
||||
|
||||
return (
|
||||
<html>
|
||||
<body>{children}</body>
|
||||
</html>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Example (preload modules for code-split routes):**
|
||||
|
||||
```tsx
|
||||
import { preloadModule, preinitModule } from 'react-dom'
|
||||
|
||||
function Navigation() {
|
||||
const preloadDashboard = () => {
|
||||
preloadModule('/dashboard.js', { as: 'script' })
|
||||
}
|
||||
|
||||
return (
|
||||
<nav>
|
||||
<a href="/dashboard" onMouseEnter={preloadDashboard}>
|
||||
Dashboard
|
||||
</a>
|
||||
</nav>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**When to use each:**
|
||||
|
||||
| API | Use case |
|
||||
|-----|----------|
|
||||
| `prefetchDNS` | Third-party domains you'll connect to later |
|
||||
| `preconnect` | APIs or CDNs you'll fetch from immediately |
|
||||
| `preload` | Critical resources needed for current page |
|
||||
| `preloadModule` | JS modules for likely next navigation |
|
||||
| `preinit` | Stylesheets/scripts that must execute early |
|
||||
| `preinitModule` | ES modules that must execute early |
|
||||
|
||||
Reference: [React DOM Resource Preloading APIs](https://react.dev/reference/react-dom#resource-preloading-apis)
|
||||
@@ -0,0 +1,68 @@
|
||||
---
|
||||
title: Use defer or async on Script Tags
|
||||
impact: HIGH
|
||||
impactDescription: eliminates render-blocking
|
||||
tags: rendering, script, defer, async, performance
|
||||
---
|
||||
|
||||
## Use defer or async on Script Tags
|
||||
|
||||
**Impact: HIGH (eliminates render-blocking)**
|
||||
|
||||
Script tags without `defer` or `async` block HTML parsing while the script downloads and executes. This delays First Contentful Paint and Time to Interactive.
|
||||
|
||||
- **`defer`**: Downloads in parallel, executes after HTML parsing completes, maintains execution order
|
||||
- **`async`**: Downloads in parallel, executes immediately when ready, no guaranteed order
|
||||
|
||||
Use `defer` for scripts that depend on DOM or other scripts. Use `async` for independent scripts like analytics.
|
||||
|
||||
**Incorrect (blocks rendering):**
|
||||
|
||||
```tsx
|
||||
export default function Document() {
|
||||
return (
|
||||
<html>
|
||||
<head>
|
||||
<script src="https://example.com/analytics.js" />
|
||||
<script src="/scripts/utils.js" />
|
||||
</head>
|
||||
<body>{/* content */}</body>
|
||||
</html>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (non-blocking):**
|
||||
|
||||
```tsx
|
||||
export default function Document() {
|
||||
return (
|
||||
<html>
|
||||
<head>
|
||||
{/* Independent script - use async */}
|
||||
<script src="https://example.com/analytics.js" async />
|
||||
{/* DOM-dependent script - use defer */}
|
||||
<script src="/scripts/utils.js" defer />
|
||||
</head>
|
||||
<body>{/* content */}</body>
|
||||
</html>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Note:** In Next.js, prefer the `next/script` component with `strategy` prop instead of raw script tags:
|
||||
|
||||
```tsx
|
||||
import Script from 'next/script'
|
||||
|
||||
export default function Page() {
|
||||
return (
|
||||
<>
|
||||
<Script src="https://example.com/analytics.js" strategy="afterInteractive" />
|
||||
<Script src="/scripts/utils.js" strategy="beforeInteractive" />
|
||||
</>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [MDN - Script element](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script#defer)
|
||||
@@ -0,0 +1,28 @@
|
||||
---
|
||||
title: Optimize SVG Precision
|
||||
impact: LOW
|
||||
impactDescription: reduces file size
|
||||
tags: rendering, svg, optimization, svgo
|
||||
---
|
||||
|
||||
## Optimize SVG Precision
|
||||
|
||||
Reduce SVG coordinate precision to decrease file size. The optimal precision depends on the viewBox size, but in general reducing precision should be considered.
|
||||
|
||||
**Incorrect (excessive precision):**
|
||||
|
||||
```svg
|
||||
<path d="M 10.293847 20.847362 L 30.938472 40.192837" />
|
||||
```
|
||||
|
||||
**Correct (1 decimal place):**
|
||||
|
||||
```svg
|
||||
<path d="M 10.3 20.8 L 30.9 40.2" />
|
||||
```
|
||||
|
||||
**Automate with SVGO:**
|
||||
|
||||
```bash
|
||||
npx svgo --precision=1 --multipass icon.svg
|
||||
```
|
||||
@@ -0,0 +1,75 @@
|
||||
---
|
||||
title: Use useTransition Over Manual Loading States
|
||||
impact: LOW
|
||||
impactDescription: reduces re-renders and improves code clarity
|
||||
tags: rendering, transitions, useTransition, loading, state
|
||||
---
|
||||
|
||||
## Use useTransition Over Manual Loading States
|
||||
|
||||
Use `useTransition` instead of manual `useState` for loading states. This provides built-in `isPending` state and automatically manages transitions.
|
||||
|
||||
**Incorrect (manual loading state):**
|
||||
|
||||
```tsx
|
||||
function SearchResults() {
|
||||
const [query, setQuery] = useState('')
|
||||
const [results, setResults] = useState([])
|
||||
const [isLoading, setIsLoading] = useState(false)
|
||||
|
||||
const handleSearch = async (value: string) => {
|
||||
setIsLoading(true)
|
||||
setQuery(value)
|
||||
const data = await fetchResults(value)
|
||||
setResults(data)
|
||||
setIsLoading(false)
|
||||
}
|
||||
|
||||
return (
|
||||
<>
|
||||
<input onChange={(e) => handleSearch(e.target.value)} />
|
||||
{isLoading && <Spinner />}
|
||||
<ResultsList results={results} />
|
||||
</>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (useTransition with built-in pending state):**
|
||||
|
||||
```tsx
|
||||
import { useTransition, useState } from 'react'
|
||||
|
||||
function SearchResults() {
|
||||
const [query, setQuery] = useState('')
|
||||
const [results, setResults] = useState([])
|
||||
const [isPending, startTransition] = useTransition()
|
||||
|
||||
const handleSearch = (value: string) => {
|
||||
setQuery(value) // Update input immediately
|
||||
|
||||
startTransition(async () => {
|
||||
// Fetch and update results
|
||||
const data = await fetchResults(value)
|
||||
setResults(data)
|
||||
})
|
||||
}
|
||||
|
||||
return (
|
||||
<>
|
||||
<input onChange={(e) => handleSearch(e.target.value)} />
|
||||
{isPending && <Spinner />}
|
||||
<ResultsList results={results} />
|
||||
</>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Benefits:**
|
||||
|
||||
- **Automatic pending state**: No need to manually manage `setIsLoading(true/false)`
|
||||
- **Error resilience**: Pending state correctly resets even if the transition throws
|
||||
- **Better responsiveness**: Keeps the UI responsive during updates
|
||||
- **Interrupt handling**: New transitions automatically cancel pending ones
|
||||
|
||||
Reference: [useTransition](https://react.dev/reference/react/useTransition)
|
||||
@@ -0,0 +1,39 @@
|
||||
---
|
||||
title: Defer State Reads to Usage Point
|
||||
impact: MEDIUM
|
||||
impactDescription: avoids unnecessary subscriptions
|
||||
tags: rerender, searchParams, localStorage, optimization
|
||||
---
|
||||
|
||||
## Defer State Reads to Usage Point
|
||||
|
||||
Don't subscribe to dynamic state (searchParams, localStorage) if you only read it inside callbacks.
|
||||
|
||||
**Incorrect (subscribes to all searchParams changes):**
|
||||
|
||||
```tsx
|
||||
function ShareButton({ chatId }: { chatId: string }) {
|
||||
const searchParams = useSearchParams()
|
||||
|
||||
const handleShare = () => {
|
||||
const ref = searchParams.get('ref')
|
||||
shareChat(chatId, { ref })
|
||||
}
|
||||
|
||||
return <button onClick={handleShare}>Share</button>
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (reads on demand, no subscription):**
|
||||
|
||||
```tsx
|
||||
function ShareButton({ chatId }: { chatId: string }) {
|
||||
const handleShare = () => {
|
||||
const params = new URLSearchParams(window.location.search)
|
||||
const ref = params.get('ref')
|
||||
shareChat(chatId, { ref })
|
||||
}
|
||||
|
||||
return <button onClick={handleShare}>Share</button>
|
||||
}
|
||||
```
|
||||
@@ -0,0 +1,45 @@
|
||||
---
|
||||
title: Narrow Effect Dependencies
|
||||
impact: LOW
|
||||
impactDescription: minimizes effect re-runs
|
||||
tags: rerender, useEffect, dependencies, optimization
|
||||
---
|
||||
|
||||
## Narrow Effect Dependencies
|
||||
|
||||
Specify primitive dependencies instead of objects to minimize effect re-runs.
|
||||
|
||||
**Incorrect (re-runs on any user field change):**
|
||||
|
||||
```tsx
|
||||
useEffect(() => {
|
||||
console.log(user.id)
|
||||
}, [user])
|
||||
```
|
||||
|
||||
**Correct (re-runs only when id changes):**
|
||||
|
||||
```tsx
|
||||
useEffect(() => {
|
||||
console.log(user.id)
|
||||
}, [user.id])
|
||||
```
|
||||
|
||||
**For derived state, compute outside effect:**
|
||||
|
||||
```tsx
|
||||
// Incorrect: runs on width=767, 766, 765...
|
||||
useEffect(() => {
|
||||
if (width < 768) {
|
||||
enableMobileMode()
|
||||
}
|
||||
}, [width])
|
||||
|
||||
// Correct: runs only on boolean transition
|
||||
const isMobile = width < 768
|
||||
useEffect(() => {
|
||||
if (isMobile) {
|
||||
enableMobileMode()
|
||||
}
|
||||
}, [isMobile])
|
||||
```
|
||||
@@ -0,0 +1,40 @@
|
||||
---
|
||||
title: Calculate Derived State During Rendering
|
||||
impact: MEDIUM
|
||||
impactDescription: avoids redundant renders and state drift
|
||||
tags: rerender, derived-state, useEffect, state
|
||||
---
|
||||
|
||||
## Calculate Derived State During Rendering
|
||||
|
||||
If a value can be computed from current props/state, do not store it in state or update it in an effect. Derive it during render to avoid extra renders and state drift. Do not set state in effects solely in response to prop changes; prefer derived values or keyed resets instead.
|
||||
|
||||
**Incorrect (redundant state and effect):**
|
||||
|
||||
```tsx
|
||||
function Form() {
|
||||
const [firstName, setFirstName] = useState('First')
|
||||
const [lastName, setLastName] = useState('Last')
|
||||
const [fullName, setFullName] = useState('')
|
||||
|
||||
useEffect(() => {
|
||||
setFullName(firstName + ' ' + lastName)
|
||||
}, [firstName, lastName])
|
||||
|
||||
return <p>{fullName}</p>
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (derive during render):**
|
||||
|
||||
```tsx
|
||||
function Form() {
|
||||
const [firstName, setFirstName] = useState('First')
|
||||
const [lastName, setLastName] = useState('Last')
|
||||
const fullName = firstName + ' ' + lastName
|
||||
|
||||
return <p>{fullName}</p>
|
||||
}
|
||||
```
|
||||
|
||||
References: [You Might Not Need an Effect](https://react.dev/learn/you-might-not-need-an-effect)
|
||||
@@ -0,0 +1,29 @@
|
||||
---
|
||||
title: Subscribe to Derived State
|
||||
impact: MEDIUM
|
||||
impactDescription: reduces re-render frequency
|
||||
tags: rerender, derived-state, media-query, optimization
|
||||
---
|
||||
|
||||
## Subscribe to Derived State
|
||||
|
||||
Subscribe to derived boolean state instead of continuous values to reduce re-render frequency.
|
||||
|
||||
**Incorrect (re-renders on every pixel change):**
|
||||
|
||||
```tsx
|
||||
function Sidebar() {
|
||||
const width = useWindowWidth() // updates continuously
|
||||
const isMobile = width < 768
|
||||
return <nav className={isMobile ? 'mobile' : 'desktop'} />
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (re-renders only when boolean changes):**
|
||||
|
||||
```tsx
|
||||
function Sidebar() {
|
||||
const isMobile = useMediaQuery('(max-width: 767px)')
|
||||
return <nav className={isMobile ? 'mobile' : 'desktop'} />
|
||||
}
|
||||
```
|
||||
@@ -0,0 +1,74 @@
|
||||
---
|
||||
title: Use Functional setState Updates
|
||||
impact: MEDIUM
|
||||
impactDescription: prevents stale closures and unnecessary callback recreations
|
||||
tags: react, hooks, useState, useCallback, callbacks, closures
|
||||
---
|
||||
|
||||
## Use Functional setState Updates
|
||||
|
||||
When updating state based on the current state value, use the functional update form of setState instead of directly referencing the state variable. This prevents stale closures, eliminates unnecessary dependencies, and creates stable callback references.
|
||||
|
||||
**Incorrect (requires state as dependency):**
|
||||
|
||||
```tsx
|
||||
function TodoList() {
|
||||
const [items, setItems] = useState(initialItems)
|
||||
|
||||
// Callback must depend on items, recreated on every items change
|
||||
const addItems = useCallback((newItems: Item[]) => {
|
||||
setItems([...items, ...newItems])
|
||||
}, [items]) // ❌ items dependency causes recreations
|
||||
|
||||
// Risk of stale closure if dependency is forgotten
|
||||
const removeItem = useCallback((id: string) => {
|
||||
setItems(items.filter(item => item.id !== id))
|
||||
}, []) // ❌ Missing items dependency - will use stale items!
|
||||
|
||||
return <ItemsEditor items={items} onAdd={addItems} onRemove={removeItem} />
|
||||
}
|
||||
```
|
||||
|
||||
The first callback is recreated every time `items` changes, which can cause child components to re-render unnecessarily. The second callback has a stale closure bug—it will always reference the initial `items` value.
|
||||
|
||||
**Correct (stable callbacks, no stale closures):**
|
||||
|
||||
```tsx
|
||||
function TodoList() {
|
||||
const [items, setItems] = useState(initialItems)
|
||||
|
||||
// Stable callback, never recreated
|
||||
const addItems = useCallback((newItems: Item[]) => {
|
||||
setItems(curr => [...curr, ...newItems])
|
||||
}, []) // ✅ No dependencies needed
|
||||
|
||||
// Always uses latest state, no stale closure risk
|
||||
const removeItem = useCallback((id: string) => {
|
||||
setItems(curr => curr.filter(item => item.id !== id))
|
||||
}, []) // ✅ Safe and stable
|
||||
|
||||
return <ItemsEditor items={items} onAdd={addItems} onRemove={removeItem} />
|
||||
}
|
||||
```
|
||||
|
||||
**Benefits:**
|
||||
|
||||
1. **Stable callback references** - Callbacks don't need to be recreated when state changes
|
||||
2. **No stale closures** - Always operates on the latest state value
|
||||
3. **Fewer dependencies** - Simplifies dependency arrays and reduces memory leaks
|
||||
4. **Prevents bugs** - Eliminates the most common source of React closure bugs
|
||||
|
||||
**When to use functional updates:**
|
||||
|
||||
- Any setState that depends on the current state value
|
||||
- Inside useCallback/useMemo when state is needed
|
||||
- Event handlers that reference state
|
||||
- Async operations that update state
|
||||
|
||||
**When direct updates are fine:**
|
||||
|
||||
- Setting state to a static value: `setCount(0)`
|
||||
- Setting state from props/arguments only: `setName(newName)`
|
||||
- State doesn't depend on previous value
|
||||
|
||||
**Note:** If your project has [React Compiler](https://react.dev/learn/react-compiler) enabled, the compiler can automatically optimize some cases, but functional updates are still recommended for correctness and to prevent stale closure bugs.
|
||||
@@ -0,0 +1,58 @@
|
||||
---
|
||||
title: Use Lazy State Initialization
|
||||
impact: MEDIUM
|
||||
impactDescription: wasted computation on every render
|
||||
tags: react, hooks, useState, performance, initialization
|
||||
---
|
||||
|
||||
## Use Lazy State Initialization
|
||||
|
||||
Pass a function to `useState` for expensive initial values. Without the function form, the initializer runs on every render even though the value is only used once.
|
||||
|
||||
**Incorrect (runs on every render):**
|
||||
|
||||
```tsx
|
||||
function FilteredList({ items }: { items: Item[] }) {
|
||||
// buildSearchIndex() runs on EVERY render, even after initialization
|
||||
const [searchIndex, setSearchIndex] = useState(buildSearchIndex(items))
|
||||
const [query, setQuery] = useState('')
|
||||
|
||||
// When query changes, buildSearchIndex runs again unnecessarily
|
||||
return <SearchResults index={searchIndex} query={query} />
|
||||
}
|
||||
|
||||
function UserProfile() {
|
||||
// JSON.parse runs on every render
|
||||
const [settings, setSettings] = useState(
|
||||
JSON.parse(localStorage.getItem('settings') || '{}')
|
||||
)
|
||||
|
||||
return <SettingsForm settings={settings} onChange={setSettings} />
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (runs only once):**
|
||||
|
||||
```tsx
|
||||
function FilteredList({ items }: { items: Item[] }) {
|
||||
// buildSearchIndex() runs ONLY on initial render
|
||||
const [searchIndex, setSearchIndex] = useState(() => buildSearchIndex(items))
|
||||
const [query, setQuery] = useState('')
|
||||
|
||||
return <SearchResults index={searchIndex} query={query} />
|
||||
}
|
||||
|
||||
function UserProfile() {
|
||||
// JSON.parse runs only on initial render
|
||||
const [settings, setSettings] = useState(() => {
|
||||
const stored = localStorage.getItem('settings')
|
||||
return stored ? JSON.parse(stored) : {}
|
||||
})
|
||||
|
||||
return <SettingsForm settings={settings} onChange={setSettings} />
|
||||
}
|
||||
```
|
||||
|
||||
Use lazy initialization when computing initial values from localStorage/sessionStorage, building data structures (indexes, maps), reading from the DOM, or performing heavy transformations.
|
||||
|
||||
For simple primitives (`useState(0)`), direct references (`useState(props.value)`), or cheap literals (`useState({})`), the function form is unnecessary.
|
||||
@@ -0,0 +1,38 @@
|
||||
---
|
||||
|
||||
title: Extract Default Non-primitive Parameter Value from Memoized Component to Constant
|
||||
impact: MEDIUM
|
||||
impactDescription: restores memoization by using a constant for default value
|
||||
tags: rerender, memo, optimization
|
||||
|
||||
---
|
||||
|
||||
## Extract Default Non-primitive Parameter Value from Memoized Component to Constant
|
||||
|
||||
When memoized component has a default value for some non-primitive optional parameter, such as an array, function, or object, calling the component without that parameter results in broken memoization. This is because new value instances are created on every rerender, and they do not pass strict equality comparison in `memo()`.
|
||||
|
||||
To address this issue, extract the default value into a constant.
|
||||
|
||||
**Incorrect (`onClick` has different values on every rerender):**
|
||||
|
||||
```tsx
|
||||
const UserAvatar = memo(function UserAvatar({ onClick = () => {} }: { onClick?: () => void }) {
|
||||
// ...
|
||||
})
|
||||
|
||||
// Used without optional onClick
|
||||
<UserAvatar />
|
||||
```
|
||||
|
||||
**Correct (stable default value):**
|
||||
|
||||
```tsx
|
||||
const NOOP = () => {};
|
||||
|
||||
const UserAvatar = memo(function UserAvatar({ onClick = NOOP }: { onClick?: () => void }) {
|
||||
// ...
|
||||
})
|
||||
|
||||
// Used without optional onClick
|
||||
<UserAvatar />
|
||||
```
|
||||
@@ -0,0 +1,44 @@
|
||||
---
|
||||
title: Extract to Memoized Components
|
||||
impact: MEDIUM
|
||||
impactDescription: enables early returns
|
||||
tags: rerender, memo, useMemo, optimization
|
||||
---
|
||||
|
||||
## Extract to Memoized Components
|
||||
|
||||
Extract expensive work into memoized components to enable early returns before computation.
|
||||
|
||||
**Incorrect (computes avatar even when loading):**
|
||||
|
||||
```tsx
|
||||
function Profile({ user, loading }: Props) {
|
||||
const avatar = useMemo(() => {
|
||||
const id = computeAvatarId(user)
|
||||
return <Avatar id={id} />
|
||||
}, [user])
|
||||
|
||||
if (loading) return <Skeleton />
|
||||
return <div>{avatar}</div>
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (skips computation when loading):**
|
||||
|
||||
```tsx
|
||||
const UserAvatar = memo(function UserAvatar({ user }: { user: User }) {
|
||||
const id = useMemo(() => computeAvatarId(user), [user])
|
||||
return <Avatar id={id} />
|
||||
})
|
||||
|
||||
function Profile({ user, loading }: Props) {
|
||||
if (loading) return <Skeleton />
|
||||
return (
|
||||
<div>
|
||||
<UserAvatar user={user} />
|
||||
</div>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Note:** If your project has [React Compiler](https://react.dev/learn/react-compiler) enabled, manual memoization with `memo()` and `useMemo()` is not necessary. The compiler automatically optimizes re-renders.
|
||||
@@ -0,0 +1,45 @@
|
||||
---
|
||||
title: Put Interaction Logic in Event Handlers
|
||||
impact: MEDIUM
|
||||
impactDescription: avoids effect re-runs and duplicate side effects
|
||||
tags: rerender, useEffect, events, side-effects, dependencies
|
||||
---
|
||||
|
||||
## Put Interaction Logic in Event Handlers
|
||||
|
||||
If a side effect is triggered by a specific user action (submit, click, drag), run it in that event handler. Do not model the action as state + effect; it makes effects re-run on unrelated changes and can duplicate the action.
|
||||
|
||||
**Incorrect (event modeled as state + effect):**
|
||||
|
||||
```tsx
|
||||
function Form() {
|
||||
const [submitted, setSubmitted] = useState(false)
|
||||
const theme = useContext(ThemeContext)
|
||||
|
||||
useEffect(() => {
|
||||
if (submitted) {
|
||||
post('/api/register')
|
||||
showToast('Registered', theme)
|
||||
}
|
||||
}, [submitted, theme])
|
||||
|
||||
return <button onClick={() => setSubmitted(true)}>Submit</button>
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (do it in the handler):**
|
||||
|
||||
```tsx
|
||||
function Form() {
|
||||
const theme = useContext(ThemeContext)
|
||||
|
||||
function handleSubmit() {
|
||||
post('/api/register')
|
||||
showToast('Registered', theme)
|
||||
}
|
||||
|
||||
return <button onClick={handleSubmit}>Submit</button>
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [Should this code move to an event handler?](https://react.dev/learn/removing-effect-dependencies#should-this-code-move-to-an-event-handler)
|
||||
@@ -0,0 +1,82 @@
|
||||
---
|
||||
title: Don't Define Components Inside Components
|
||||
impact: HIGH
|
||||
impactDescription: prevents remount on every render
|
||||
tags: rerender, components, remount, performance
|
||||
---
|
||||
|
||||
## Don't Define Components Inside Components
|
||||
|
||||
**Impact: HIGH (prevents remount on every render)**
|
||||
|
||||
Defining a component inside another component creates a new component type on every render. React sees a different component each time and fully remounts it, destroying all state and DOM.
|
||||
|
||||
A common reason developers do this is to access parent variables without passing props. Always pass props instead.
|
||||
|
||||
**Incorrect (remounts on every render):**
|
||||
|
||||
```tsx
|
||||
function UserProfile({ user, theme }) {
|
||||
// Defined inside to access `theme` - BAD
|
||||
const Avatar = () => (
|
||||
<img
|
||||
src={user.avatarUrl}
|
||||
className={theme === 'dark' ? 'avatar-dark' : 'avatar-light'}
|
||||
/>
|
||||
)
|
||||
|
||||
// Defined inside to access `user` - BAD
|
||||
const Stats = () => (
|
||||
<div>
|
||||
<span>{user.followers} followers</span>
|
||||
<span>{user.posts} posts</span>
|
||||
</div>
|
||||
)
|
||||
|
||||
return (
|
||||
<div>
|
||||
<Avatar />
|
||||
<Stats />
|
||||
</div>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
Every time `UserProfile` renders, `Avatar` and `Stats` are new component types. React unmounts the old instances and mounts new ones, losing any internal state, running effects again, and recreating DOM nodes.
|
||||
|
||||
**Correct (pass props instead):**
|
||||
|
||||
```tsx
|
||||
function Avatar({ src, theme }: { src: string; theme: string }) {
|
||||
return (
|
||||
<img
|
||||
src={src}
|
||||
className={theme === 'dark' ? 'avatar-dark' : 'avatar-light'}
|
||||
/>
|
||||
)
|
||||
}
|
||||
|
||||
function Stats({ followers, posts }: { followers: number; posts: number }) {
|
||||
return (
|
||||
<div>
|
||||
<span>{followers} followers</span>
|
||||
<span>{posts} posts</span>
|
||||
</div>
|
||||
)
|
||||
}
|
||||
|
||||
function UserProfile({ user, theme }) {
|
||||
return (
|
||||
<div>
|
||||
<Avatar src={user.avatarUrl} theme={theme} />
|
||||
<Stats followers={user.followers} posts={user.posts} />
|
||||
</div>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Symptoms of this bug:**
|
||||
- Input fields lose focus on every keystroke
|
||||
- Animations restart unexpectedly
|
||||
- `useEffect` cleanup/setup runs on every parent render
|
||||
- Scroll position resets inside the component
|
||||
+35
@@ -0,0 +1,35 @@
|
||||
---
|
||||
title: Do not wrap a simple expression with a primitive result type in useMemo
|
||||
impact: LOW-MEDIUM
|
||||
impactDescription: wasted computation on every render
|
||||
tags: rerender, useMemo, optimization
|
||||
---
|
||||
|
||||
## Do not wrap a simple expression with a primitive result type in useMemo
|
||||
|
||||
When an expression is simple (few logical or arithmetical operators) and has a primitive result type (boolean, number, string), do not wrap it in `useMemo`.
|
||||
Calling `useMemo` and comparing hook dependencies may consume more resources than the expression itself.
|
||||
|
||||
**Incorrect:**
|
||||
|
||||
```tsx
|
||||
function Header({ user, notifications }: Props) {
|
||||
const isLoading = useMemo(() => {
|
||||
return user.isLoading || notifications.isLoading
|
||||
}, [user.isLoading, notifications.isLoading])
|
||||
|
||||
if (isLoading) return <Skeleton />
|
||||
// return some markup
|
||||
}
|
||||
```
|
||||
|
||||
**Correct:**
|
||||
|
||||
```tsx
|
||||
function Header({ user, notifications }: Props) {
|
||||
const isLoading = user.isLoading || notifications.isLoading
|
||||
|
||||
if (isLoading) return <Skeleton />
|
||||
// return some markup
|
||||
}
|
||||
```
|
||||
@@ -0,0 +1,64 @@
|
||||
---
|
||||
title: Split Combined Hook Computations
|
||||
impact: MEDIUM
|
||||
impactDescription: avoids recomputing independent steps
|
||||
tags: rerender, useMemo, useEffect, dependencies, optimization
|
||||
---
|
||||
|
||||
## Split Combined Hook Computations
|
||||
|
||||
When a hook contains multiple independent tasks with different dependencies, split them into separate hooks. A combined hook reruns all tasks when any dependency changes, even if some tasks don't use the changed value.
|
||||
|
||||
**Incorrect (changing `sortOrder` recomputes filtering):**
|
||||
|
||||
```tsx
|
||||
const sortedProducts = useMemo(() => {
|
||||
const filtered = products.filter((p) => p.category === category)
|
||||
const sorted = filtered.toSorted((a, b) =>
|
||||
sortOrder === "asc" ? a.price - b.price : b.price - a.price
|
||||
)
|
||||
return sorted
|
||||
}, [products, category, sortOrder])
|
||||
```
|
||||
|
||||
**Correct (filtering only recomputes when products or category change):**
|
||||
|
||||
```tsx
|
||||
const filteredProducts = useMemo(
|
||||
() => products.filter((p) => p.category === category),
|
||||
[products, category]
|
||||
)
|
||||
|
||||
const sortedProducts = useMemo(
|
||||
() =>
|
||||
filteredProducts.toSorted((a, b) =>
|
||||
sortOrder === "asc" ? a.price - b.price : b.price - a.price
|
||||
),
|
||||
[filteredProducts, sortOrder]
|
||||
)
|
||||
```
|
||||
|
||||
This pattern also applies to `useEffect` when combining unrelated side effects:
|
||||
|
||||
**Incorrect (both effects run when either dependency changes):**
|
||||
|
||||
```tsx
|
||||
useEffect(() => {
|
||||
analytics.trackPageView(pathname)
|
||||
document.title = `${pageTitle} | My App`
|
||||
}, [pathname, pageTitle])
|
||||
```
|
||||
|
||||
**Correct (effects run independently):**
|
||||
|
||||
```tsx
|
||||
useEffect(() => {
|
||||
analytics.trackPageView(pathname)
|
||||
}, [pathname])
|
||||
|
||||
useEffect(() => {
|
||||
document.title = `${pageTitle} | My App`
|
||||
}, [pageTitle])
|
||||
```
|
||||
|
||||
**Note:** If your project has [React Compiler](https://react.dev/learn/react-compiler) enabled, it automatically optimizes dependency tracking and may handle some of these cases for you.
|
||||
@@ -0,0 +1,40 @@
|
||||
---
|
||||
title: Use Transitions for Non-Urgent Updates
|
||||
impact: MEDIUM
|
||||
impactDescription: maintains UI responsiveness
|
||||
tags: rerender, transitions, startTransition, performance
|
||||
---
|
||||
|
||||
## Use Transitions for Non-Urgent Updates
|
||||
|
||||
Mark frequent, non-urgent state updates as transitions to maintain UI responsiveness.
|
||||
|
||||
**Incorrect (blocks UI on every scroll):**
|
||||
|
||||
```tsx
|
||||
function ScrollTracker() {
|
||||
const [scrollY, setScrollY] = useState(0)
|
||||
useEffect(() => {
|
||||
const handler = () => setScrollY(window.scrollY)
|
||||
window.addEventListener('scroll', handler, { passive: true })
|
||||
return () => window.removeEventListener('scroll', handler)
|
||||
}, [])
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (non-blocking updates):**
|
||||
|
||||
```tsx
|
||||
import { startTransition } from 'react'
|
||||
|
||||
function ScrollTracker() {
|
||||
const [scrollY, setScrollY] = useState(0)
|
||||
useEffect(() => {
|
||||
const handler = () => {
|
||||
startTransition(() => setScrollY(window.scrollY))
|
||||
}
|
||||
window.addEventListener('scroll', handler, { passive: true })
|
||||
return () => window.removeEventListener('scroll', handler)
|
||||
}, [])
|
||||
}
|
||||
```
|
||||
@@ -0,0 +1,59 @@
|
||||
---
|
||||
title: Use useDeferredValue for Expensive Derived Renders
|
||||
impact: MEDIUM
|
||||
impactDescription: keeps input responsive during heavy computation
|
||||
tags: rerender, useDeferredValue, optimization, concurrent
|
||||
---
|
||||
|
||||
## Use useDeferredValue for Expensive Derived Renders
|
||||
|
||||
When user input triggers expensive computations or renders, use `useDeferredValue` to keep the input responsive. The deferred value lags behind, allowing React to prioritize the input update and render the expensive result when idle.
|
||||
|
||||
**Incorrect (input feels laggy while filtering):**
|
||||
|
||||
```tsx
|
||||
function Search({ items }: { items: Item[] }) {
|
||||
const [query, setQuery] = useState('')
|
||||
const filtered = items.filter(item => fuzzyMatch(item, query))
|
||||
|
||||
return (
|
||||
<>
|
||||
<input value={query} onChange={e => setQuery(e.target.value)} />
|
||||
<ResultsList results={filtered} />
|
||||
</>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (input stays snappy, results render when ready):**
|
||||
|
||||
```tsx
|
||||
function Search({ items }: { items: Item[] }) {
|
||||
const [query, setQuery] = useState('')
|
||||
const deferredQuery = useDeferredValue(query)
|
||||
const filtered = useMemo(
|
||||
() => items.filter(item => fuzzyMatch(item, deferredQuery)),
|
||||
[items, deferredQuery]
|
||||
)
|
||||
const isStale = query !== deferredQuery
|
||||
|
||||
return (
|
||||
<>
|
||||
<input value={query} onChange={e => setQuery(e.target.value)} />
|
||||
<div style={{ opacity: isStale ? 0.7 : 1 }}>
|
||||
<ResultsList results={filtered} />
|
||||
</div>
|
||||
</>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**When to use:**
|
||||
|
||||
- Filtering/searching large lists
|
||||
- Expensive visualizations (charts, graphs) reacting to input
|
||||
- Any derived state that causes noticeable render delays
|
||||
|
||||
**Note:** Wrap the expensive computation in `useMemo` with the deferred value as a dependency, otherwise it still runs on every render.
|
||||
|
||||
Reference: [React useDeferredValue](https://react.dev/reference/react/useDeferredValue)
|
||||
@@ -0,0 +1,73 @@
|
||||
---
|
||||
title: Use useRef for Transient Values
|
||||
impact: MEDIUM
|
||||
impactDescription: avoids unnecessary re-renders on frequent updates
|
||||
tags: rerender, useref, state, performance
|
||||
---
|
||||
|
||||
## Use useRef for Transient Values
|
||||
|
||||
When a value changes frequently and you don't want a re-render on every update (e.g., mouse trackers, intervals, transient flags), store it in `useRef` instead of `useState`. Keep component state for UI; use refs for temporary DOM-adjacent values. Updating a ref does not trigger a re-render.
|
||||
|
||||
**Incorrect (renders every update):**
|
||||
|
||||
```tsx
|
||||
function Tracker() {
|
||||
const [lastX, setLastX] = useState(0)
|
||||
|
||||
useEffect(() => {
|
||||
const onMove = (e: MouseEvent) => setLastX(e.clientX)
|
||||
window.addEventListener('mousemove', onMove)
|
||||
return () => window.removeEventListener('mousemove', onMove)
|
||||
}, [])
|
||||
|
||||
return (
|
||||
<div
|
||||
style={{
|
||||
position: 'fixed',
|
||||
top: 0,
|
||||
left: lastX,
|
||||
width: 8,
|
||||
height: 8,
|
||||
background: 'black',
|
||||
}}
|
||||
/>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (no re-render for tracking):**
|
||||
|
||||
```tsx
|
||||
function Tracker() {
|
||||
const lastXRef = useRef(0)
|
||||
const dotRef = useRef<HTMLDivElement>(null)
|
||||
|
||||
useEffect(() => {
|
||||
const onMove = (e: MouseEvent) => {
|
||||
lastXRef.current = e.clientX
|
||||
const node = dotRef.current
|
||||
if (node) {
|
||||
node.style.transform = `translateX(${e.clientX}px)`
|
||||
}
|
||||
}
|
||||
window.addEventListener('mousemove', onMove)
|
||||
return () => window.removeEventListener('mousemove', onMove)
|
||||
}, [])
|
||||
|
||||
return (
|
||||
<div
|
||||
ref={dotRef}
|
||||
style={{
|
||||
position: 'fixed',
|
||||
top: 0,
|
||||
left: 0,
|
||||
width: 8,
|
||||
height: 8,
|
||||
background: 'black',
|
||||
transform: 'translateX(0px)',
|
||||
}}
|
||||
/>
|
||||
)
|
||||
}
|
||||
```
|
||||
@@ -0,0 +1,73 @@
|
||||
---
|
||||
title: Use after() for Non-Blocking Operations
|
||||
impact: MEDIUM
|
||||
impactDescription: faster response times
|
||||
tags: server, async, logging, analytics, side-effects
|
||||
---
|
||||
|
||||
## Use after() for Non-Blocking Operations
|
||||
|
||||
Use Next.js's `after()` to schedule work that should execute after a response is sent. This prevents logging, analytics, and other side effects from blocking the response.
|
||||
|
||||
**Incorrect (blocks response):**
|
||||
|
||||
```tsx
|
||||
import { logUserAction } from '@/app/utils'
|
||||
|
||||
export async function POST(request: Request) {
|
||||
// Perform mutation
|
||||
await updateDatabase(request)
|
||||
|
||||
// Logging blocks the response
|
||||
const userAgent = request.headers.get('user-agent') || 'unknown'
|
||||
await logUserAction({ userAgent })
|
||||
|
||||
return new Response(JSON.stringify({ status: 'success' }), {
|
||||
status: 200,
|
||||
headers: { 'Content-Type': 'application/json' }
|
||||
})
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (non-blocking):**
|
||||
|
||||
```tsx
|
||||
import { after } from 'next/server'
|
||||
import { headers, cookies } from 'next/headers'
|
||||
import { logUserAction } from '@/app/utils'
|
||||
|
||||
export async function POST(request: Request) {
|
||||
// Perform mutation
|
||||
await updateDatabase(request)
|
||||
|
||||
// Log after response is sent
|
||||
after(async () => {
|
||||
const userAgent = (await headers()).get('user-agent') || 'unknown'
|
||||
const sessionCookie = (await cookies()).get('session-id')?.value || 'anonymous'
|
||||
|
||||
logUserAction({ sessionCookie, userAgent })
|
||||
})
|
||||
|
||||
return new Response(JSON.stringify({ status: 'success' }), {
|
||||
status: 200,
|
||||
headers: { 'Content-Type': 'application/json' }
|
||||
})
|
||||
}
|
||||
```
|
||||
|
||||
The response is sent immediately while logging happens in the background.
|
||||
|
||||
**Common use cases:**
|
||||
|
||||
- Analytics tracking
|
||||
- Audit logging
|
||||
- Sending notifications
|
||||
- Cache invalidation
|
||||
- Cleanup tasks
|
||||
|
||||
**Important notes:**
|
||||
|
||||
- `after()` runs even if the response fails or redirects
|
||||
- Works in Server Actions, Route Handlers, and Server Components
|
||||
|
||||
Reference: [https://nextjs.org/docs/app/api-reference/functions/after](https://nextjs.org/docs/app/api-reference/functions/after)
|
||||
@@ -0,0 +1,96 @@
|
||||
---
|
||||
title: Authenticate Server Actions Like API Routes
|
||||
impact: CRITICAL
|
||||
impactDescription: prevents unauthorized access to server mutations
|
||||
tags: server, server-actions, authentication, security, authorization
|
||||
---
|
||||
|
||||
## Authenticate Server Actions Like API Routes
|
||||
|
||||
**Impact: CRITICAL (prevents unauthorized access to server mutations)**
|
||||
|
||||
Server Actions (functions with `"use server"`) are exposed as public endpoints, just like API routes. Always verify authentication and authorization **inside** each Server Action—do not rely solely on middleware, layout guards, or page-level checks, as Server Actions can be invoked directly.
|
||||
|
||||
Next.js documentation explicitly states: "Treat Server Actions with the same security considerations as public-facing API endpoints, and verify if the user is allowed to perform a mutation."
|
||||
|
||||
**Incorrect (no authentication check):**
|
||||
|
||||
```typescript
|
||||
'use server'
|
||||
|
||||
export async function deleteUser(userId: string) {
|
||||
// Anyone can call this! No auth check
|
||||
await db.user.delete({ where: { id: userId } })
|
||||
return { success: true }
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (authentication inside the action):**
|
||||
|
||||
```typescript
|
||||
'use server'
|
||||
|
||||
import { verifySession } from '@/lib/auth'
|
||||
import { unauthorized } from '@/lib/errors'
|
||||
|
||||
export async function deleteUser(userId: string) {
|
||||
// Always check auth inside the action
|
||||
const session = await verifySession()
|
||||
|
||||
if (!session) {
|
||||
throw unauthorized('Must be logged in')
|
||||
}
|
||||
|
||||
// Check authorization too
|
||||
if (session.user.role !== 'admin' && session.user.id !== userId) {
|
||||
throw unauthorized('Cannot delete other users')
|
||||
}
|
||||
|
||||
await db.user.delete({ where: { id: userId } })
|
||||
return { success: true }
|
||||
}
|
||||
```
|
||||
|
||||
**With input validation:**
|
||||
|
||||
```typescript
|
||||
'use server'
|
||||
|
||||
import { verifySession } from '@/lib/auth'
|
||||
import { z } from 'zod'
|
||||
|
||||
const updateProfileSchema = z.object({
|
||||
userId: z.string().uuid(),
|
||||
name: z.string().min(1).max(100),
|
||||
email: z.string().email()
|
||||
})
|
||||
|
||||
export async function updateProfile(data: unknown) {
|
||||
// Validate input first
|
||||
const validated = updateProfileSchema.parse(data)
|
||||
|
||||
// Then authenticate
|
||||
const session = await verifySession()
|
||||
if (!session) {
|
||||
throw new Error('Unauthorized')
|
||||
}
|
||||
|
||||
// Then authorize
|
||||
if (session.user.id !== validated.userId) {
|
||||
throw new Error('Can only update own profile')
|
||||
}
|
||||
|
||||
// Finally perform the mutation
|
||||
await db.user.update({
|
||||
where: { id: validated.userId },
|
||||
data: {
|
||||
name: validated.name,
|
||||
email: validated.email
|
||||
}
|
||||
})
|
||||
|
||||
return { success: true }
|
||||
}
|
||||
```
|
||||
|
||||
Reference: [https://nextjs.org/docs/app/guides/authentication](https://nextjs.org/docs/app/guides/authentication)
|
||||
@@ -0,0 +1,41 @@
|
||||
---
|
||||
title: Cross-Request LRU Caching
|
||||
impact: HIGH
|
||||
impactDescription: caches across requests
|
||||
tags: server, cache, lru, cross-request
|
||||
---
|
||||
|
||||
## Cross-Request LRU Caching
|
||||
|
||||
`React.cache()` only works within one request. For data shared across sequential requests (user clicks button A then button B), use an LRU cache.
|
||||
|
||||
**Implementation:**
|
||||
|
||||
```typescript
|
||||
import { LRUCache } from 'lru-cache'
|
||||
|
||||
const cache = new LRUCache<string, any>({
|
||||
max: 1000,
|
||||
ttl: 5 * 60 * 1000 // 5 minutes
|
||||
})
|
||||
|
||||
export async function getUser(id: string) {
|
||||
const cached = cache.get(id)
|
||||
if (cached) return cached
|
||||
|
||||
const user = await db.user.findUnique({ where: { id } })
|
||||
cache.set(id, user)
|
||||
return user
|
||||
}
|
||||
|
||||
// Request 1: DB query, result cached
|
||||
// Request 2: cache hit, no DB query
|
||||
```
|
||||
|
||||
Use when sequential user actions hit multiple endpoints needing the same data within seconds.
|
||||
|
||||
**With Vercel's [Fluid Compute](https://vercel.com/docs/fluid-compute):** LRU caching is especially effective because multiple concurrent requests can share the same function instance and cache. This means the cache persists across requests without needing external storage like Redis.
|
||||
|
||||
**In traditional serverless:** Each invocation runs in isolation, so consider Redis for cross-process caching.
|
||||
|
||||
Reference: [https://github.com/isaacs/node-lru-cache](https://github.com/isaacs/node-lru-cache)
|
||||
@@ -0,0 +1,76 @@
|
||||
---
|
||||
title: Per-Request Deduplication with React.cache()
|
||||
impact: MEDIUM
|
||||
impactDescription: deduplicates within request
|
||||
tags: server, cache, react-cache, deduplication
|
||||
---
|
||||
|
||||
## Per-Request Deduplication with React.cache()
|
||||
|
||||
Use `React.cache()` for server-side request deduplication. Authentication and database queries benefit most.
|
||||
|
||||
**Usage:**
|
||||
|
||||
```typescript
|
||||
import { cache } from 'react'
|
||||
|
||||
export const getCurrentUser = cache(async () => {
|
||||
const session = await auth()
|
||||
if (!session?.user?.id) return null
|
||||
return await db.user.findUnique({
|
||||
where: { id: session.user.id }
|
||||
})
|
||||
})
|
||||
```
|
||||
|
||||
Within a single request, multiple calls to `getCurrentUser()` execute the query only once.
|
||||
|
||||
**Avoid inline objects as arguments:**
|
||||
|
||||
`React.cache()` uses shallow equality (`Object.is`) to determine cache hits. Inline objects create new references each call, preventing cache hits.
|
||||
|
||||
**Incorrect (always cache miss):**
|
||||
|
||||
```typescript
|
||||
const getUser = cache(async (params: { uid: number }) => {
|
||||
return await db.user.findUnique({ where: { id: params.uid } })
|
||||
})
|
||||
|
||||
// Each call creates new object, never hits cache
|
||||
getUser({ uid: 1 })
|
||||
getUser({ uid: 1 }) // Cache miss, runs query again
|
||||
```
|
||||
|
||||
**Correct (cache hit):**
|
||||
|
||||
```typescript
|
||||
const getUser = cache(async (uid: number) => {
|
||||
return await db.user.findUnique({ where: { id: uid } })
|
||||
})
|
||||
|
||||
// Primitive args use value equality
|
||||
getUser(1)
|
||||
getUser(1) // Cache hit, returns cached result
|
||||
```
|
||||
|
||||
If you must pass objects, pass the same reference:
|
||||
|
||||
```typescript
|
||||
const params = { uid: 1 }
|
||||
getUser(params) // Query runs
|
||||
getUser(params) // Cache hit (same reference)
|
||||
```
|
||||
|
||||
**Next.js-Specific Note:**
|
||||
|
||||
In Next.js, the `fetch` API is automatically extended with request memoization. Requests with the same URL and options are automatically deduplicated within a single request, so you don't need `React.cache()` for `fetch` calls. However, `React.cache()` is still essential for other async tasks:
|
||||
|
||||
- Database queries (Prisma, Drizzle, etc.)
|
||||
- Heavy computations
|
||||
- Authentication checks
|
||||
- File system operations
|
||||
- Any non-fetch async work
|
||||
|
||||
Use `React.cache()` to deduplicate these operations across your component tree.
|
||||
|
||||
Reference: [React.cache documentation](https://react.dev/reference/react/cache)
|
||||
@@ -0,0 +1,65 @@
|
||||
---
|
||||
title: Avoid Duplicate Serialization in RSC Props
|
||||
impact: LOW
|
||||
impactDescription: reduces network payload by avoiding duplicate serialization
|
||||
tags: server, rsc, serialization, props, client-components
|
||||
---
|
||||
|
||||
## Avoid Duplicate Serialization in RSC Props
|
||||
|
||||
**Impact: LOW (reduces network payload by avoiding duplicate serialization)**
|
||||
|
||||
RSC→client serialization deduplicates by object reference, not value. Same reference = serialized once; new reference = serialized again. Do transformations (`.toSorted()`, `.filter()`, `.map()`) in client, not server.
|
||||
|
||||
**Incorrect (duplicates array):**
|
||||
|
||||
```tsx
|
||||
// RSC: sends 6 strings (2 arrays × 3 items)
|
||||
<ClientList usernames={usernames} usernamesOrdered={usernames.toSorted()} />
|
||||
```
|
||||
|
||||
**Correct (sends 3 strings):**
|
||||
|
||||
```tsx
|
||||
// RSC: send once
|
||||
<ClientList usernames={usernames} />
|
||||
|
||||
// Client: transform there
|
||||
'use client'
|
||||
const sorted = useMemo(() => [...usernames].sort(), [usernames])
|
||||
```
|
||||
|
||||
**Nested deduplication behavior:**
|
||||
|
||||
Deduplication works recursively. Impact varies by data type:
|
||||
|
||||
- `string[]`, `number[]`, `boolean[]`: **HIGH impact** - array + all primitives fully duplicated
|
||||
- `object[]`: **LOW impact** - array duplicated, but nested objects deduplicated by reference
|
||||
|
||||
```tsx
|
||||
// string[] - duplicates everything
|
||||
usernames={['a','b']} sorted={usernames.toSorted()} // sends 4 strings
|
||||
|
||||
// object[] - duplicates array structure only
|
||||
users={[{id:1},{id:2}]} sorted={users.toSorted()} // sends 2 arrays + 2 unique objects (not 4)
|
||||
```
|
||||
|
||||
**Operations breaking deduplication (create new references):**
|
||||
|
||||
- Arrays: `.toSorted()`, `.filter()`, `.map()`, `.slice()`, `[...arr]`
|
||||
- Objects: `{...obj}`, `Object.assign()`, `structuredClone()`, `JSON.parse(JSON.stringify())`
|
||||
|
||||
**More examples:**
|
||||
|
||||
```tsx
|
||||
// ❌ Bad
|
||||
<C users={users} active={users.filter(u => u.active)} />
|
||||
<C product={product} productName={product.name} />
|
||||
|
||||
// ✅ Good
|
||||
<C users={users} />
|
||||
<C product={product} />
|
||||
// Do filtering/destructuring in client
|
||||
```
|
||||
|
||||
**Exception:** Pass derived data when transformation is expensive or client doesn't need original.
|
||||
@@ -0,0 +1,149 @@
|
||||
---
|
||||
title: Hoist Static I/O to Module Level
|
||||
impact: HIGH
|
||||
impactDescription: avoids repeated file/network I/O per request
|
||||
tags: server, io, performance, next.js, route-handlers, og-image
|
||||
---
|
||||
|
||||
## Hoist Static I/O to Module Level
|
||||
|
||||
**Impact: HIGH (avoids repeated file/network I/O per request)**
|
||||
|
||||
When loading static assets (fonts, logos, images, config files) in route handlers or server functions, hoist the I/O operation to module level. Module-level code runs once when the module is first imported, not on every request. This eliminates redundant file system reads or network fetches that would otherwise run on every invocation.
|
||||
|
||||
**Incorrect (reads font file on every request):**
|
||||
|
||||
```typescript
|
||||
// app/api/og/route.tsx
|
||||
import { ImageResponse } from 'next/og'
|
||||
|
||||
export async function GET(request: Request) {
|
||||
// Runs on EVERY request - expensive!
|
||||
const fontData = await fetch(
|
||||
new URL('./fonts/Inter.ttf', import.meta.url)
|
||||
).then(res => res.arrayBuffer())
|
||||
|
||||
const logoData = await fetch(
|
||||
new URL('./images/logo.png', import.meta.url)
|
||||
).then(res => res.arrayBuffer())
|
||||
|
||||
return new ImageResponse(
|
||||
<div style={{ fontFamily: 'Inter' }}>
|
||||
<img src={logoData} />
|
||||
Hello World
|
||||
</div>,
|
||||
{ fonts: [{ name: 'Inter', data: fontData }] }
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (loads once at module initialization):**
|
||||
|
||||
```typescript
|
||||
// app/api/og/route.tsx
|
||||
import { ImageResponse } from 'next/og'
|
||||
|
||||
// Module-level: runs ONCE when module is first imported
|
||||
const fontData = fetch(
|
||||
new URL('./fonts/Inter.ttf', import.meta.url)
|
||||
).then(res => res.arrayBuffer())
|
||||
|
||||
const logoData = fetch(
|
||||
new URL('./images/logo.png', import.meta.url)
|
||||
).then(res => res.arrayBuffer())
|
||||
|
||||
export async function GET(request: Request) {
|
||||
// Await the already-started promises
|
||||
const [font, logo] = await Promise.all([fontData, logoData])
|
||||
|
||||
return new ImageResponse(
|
||||
<div style={{ fontFamily: 'Inter' }}>
|
||||
<img src={logo} />
|
||||
Hello World
|
||||
</div>,
|
||||
{ fonts: [{ name: 'Inter', data: font }] }
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (synchronous fs at module level):**
|
||||
|
||||
```typescript
|
||||
// app/api/og/route.tsx
|
||||
import { ImageResponse } from 'next/og'
|
||||
import { readFileSync } from 'fs'
|
||||
import { join } from 'path'
|
||||
|
||||
// Synchronous read at module level - blocks only during module init
|
||||
const fontData = readFileSync(
|
||||
join(process.cwd(), 'public/fonts/Inter.ttf')
|
||||
)
|
||||
|
||||
const logoData = readFileSync(
|
||||
join(process.cwd(), 'public/images/logo.png')
|
||||
)
|
||||
|
||||
export async function GET(request: Request) {
|
||||
return new ImageResponse(
|
||||
<div style={{ fontFamily: 'Inter' }}>
|
||||
<img src={logoData} />
|
||||
Hello World
|
||||
</div>,
|
||||
{ fonts: [{ name: 'Inter', data: fontData }] }
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Incorrect (reads config on every call):**
|
||||
|
||||
```typescript
|
||||
import fs from 'node:fs/promises'
|
||||
|
||||
export async function processRequest(data: Data) {
|
||||
const config = JSON.parse(
|
||||
await fs.readFile('./config.json', 'utf-8')
|
||||
)
|
||||
const template = await fs.readFile('./template.html', 'utf-8')
|
||||
|
||||
return render(template, data, config)
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (hoists config and template to module level):**
|
||||
|
||||
```typescript
|
||||
import fs from 'node:fs/promises'
|
||||
|
||||
const configPromise = fs
|
||||
.readFile('./config.json', 'utf-8')
|
||||
.then(JSON.parse)
|
||||
const templatePromise = fs.readFile('./template.html', 'utf-8')
|
||||
|
||||
export async function processRequest(data: Data) {
|
||||
const [config, template] = await Promise.all([
|
||||
configPromise,
|
||||
templatePromise,
|
||||
])
|
||||
|
||||
return render(template, data, config)
|
||||
}
|
||||
```
|
||||
|
||||
When to use this pattern:
|
||||
|
||||
- Loading fonts for OG image generation
|
||||
- Loading static logos, icons, or watermarks
|
||||
- Reading configuration files that don't change at runtime
|
||||
- Loading email templates or other static templates
|
||||
- Any static asset that's the same across all requests
|
||||
|
||||
When not to use this pattern:
|
||||
|
||||
- Assets that vary per request or user
|
||||
- Files that may change during runtime (use caching with TTL instead)
|
||||
- Large files that would consume too much memory if kept loaded
|
||||
- Sensitive data that shouldn't persist in memory
|
||||
|
||||
With Vercel's [Fluid Compute](https://vercel.com/docs/fluid-compute), module-level caching is especially effective because multiple concurrent requests share the same function instance. The static assets stay loaded in memory across requests without cold start penalties.
|
||||
|
||||
In traditional serverless, each cold start re-executes module-level code, but subsequent warm invocations reuse the loaded assets until the instance is recycled.
|
||||
@@ -0,0 +1,50 @@
|
||||
---
|
||||
title: Avoid Shared Module State for Request Data
|
||||
impact: HIGH
|
||||
impactDescription: prevents concurrency bugs and request data leaks
|
||||
tags: server, rsc, ssr, concurrency, security, state
|
||||
---
|
||||
|
||||
## Avoid Shared Module State for Request Data
|
||||
|
||||
For React Server Components and client components rendered during SSR, avoid using mutable module-level variables to share request-scoped data. Server renders can run concurrently in the same process. If one render writes to shared module state and another render reads it, you can get race conditions, cross-request contamination, and security bugs where one user's data appears in another user's response.
|
||||
|
||||
Treat module scope on the server as process-wide shared memory, not request-local state.
|
||||
|
||||
**Incorrect (request data leaks across concurrent renders):**
|
||||
|
||||
```tsx
|
||||
let currentUser: User | null = null
|
||||
|
||||
export default async function Page() {
|
||||
currentUser = await auth()
|
||||
return <Dashboard />
|
||||
}
|
||||
|
||||
async function Dashboard() {
|
||||
return <div>{currentUser?.name}</div>
|
||||
}
|
||||
```
|
||||
|
||||
If two requests overlap, request A can set `currentUser`, then request B overwrites it before request A finishes rendering `Dashboard`.
|
||||
|
||||
**Correct (keep request data local to the render tree):**
|
||||
|
||||
```tsx
|
||||
export default async function Page() {
|
||||
const user = await auth()
|
||||
return <Dashboard user={user} />
|
||||
}
|
||||
|
||||
function Dashboard({ user }: { user: User | null }) {
|
||||
return <div>{user?.name}</div>
|
||||
}
|
||||
```
|
||||
|
||||
Safe exceptions:
|
||||
|
||||
- Immutable static assets or config loaded once at module scope
|
||||
- Shared caches intentionally designed for cross-request reuse and keyed correctly
|
||||
- Process-wide singletons that do not store request- or user-specific mutable data
|
||||
|
||||
For static assets and config, see [Hoist Static I/O to Module Level](./server-hoist-static-io.md).
|
||||
@@ -0,0 +1,83 @@
|
||||
---
|
||||
title: Parallel Data Fetching with Component Composition
|
||||
impact: CRITICAL
|
||||
impactDescription: eliminates server-side waterfalls
|
||||
tags: server, rsc, parallel-fetching, composition
|
||||
---
|
||||
|
||||
## Parallel Data Fetching with Component Composition
|
||||
|
||||
React Server Components execute sequentially within a tree. Restructure with composition to parallelize data fetching.
|
||||
|
||||
**Incorrect (Sidebar waits for Page's fetch to complete):**
|
||||
|
||||
```tsx
|
||||
export default async function Page() {
|
||||
const header = await fetchHeader()
|
||||
return (
|
||||
<div>
|
||||
<div>{header}</div>
|
||||
<Sidebar />
|
||||
</div>
|
||||
)
|
||||
}
|
||||
|
||||
async function Sidebar() {
|
||||
const items = await fetchSidebarItems()
|
||||
return <nav>{items.map(renderItem)}</nav>
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (both fetch simultaneously):**
|
||||
|
||||
```tsx
|
||||
async function Header() {
|
||||
const data = await fetchHeader()
|
||||
return <div>{data}</div>
|
||||
}
|
||||
|
||||
async function Sidebar() {
|
||||
const items = await fetchSidebarItems()
|
||||
return <nav>{items.map(renderItem)}</nav>
|
||||
}
|
||||
|
||||
export default function Page() {
|
||||
return (
|
||||
<div>
|
||||
<Header />
|
||||
<Sidebar />
|
||||
</div>
|
||||
)
|
||||
}
|
||||
```
|
||||
|
||||
**Alternative with children prop:**
|
||||
|
||||
```tsx
|
||||
async function Header() {
|
||||
const data = await fetchHeader()
|
||||
return <div>{data}</div>
|
||||
}
|
||||
|
||||
async function Sidebar() {
|
||||
const items = await fetchSidebarItems()
|
||||
return <nav>{items.map(renderItem)}</nav>
|
||||
}
|
||||
|
||||
function Layout({ children }: { children: ReactNode }) {
|
||||
return (
|
||||
<div>
|
||||
<Header />
|
||||
{children}
|
||||
</div>
|
||||
)
|
||||
}
|
||||
|
||||
export default function Page() {
|
||||
return (
|
||||
<Layout>
|
||||
<Sidebar />
|
||||
</Layout>
|
||||
)
|
||||
}
|
||||
```
|
||||
@@ -0,0 +1,34 @@
|
||||
---
|
||||
title: Parallel Nested Data Fetching
|
||||
impact: CRITICAL
|
||||
impactDescription: eliminates server-side waterfalls
|
||||
tags: server, rsc, parallel-fetching, promise-chaining
|
||||
---
|
||||
|
||||
## Parallel Nested Data Fetching
|
||||
|
||||
When fetching nested data in parallel, chain dependent fetches within each item's promise so a slow item doesn't block the rest.
|
||||
|
||||
**Incorrect (a single slow item blocks all nested fetches):**
|
||||
|
||||
```tsx
|
||||
const chats = await Promise.all(
|
||||
chatIds.map(id => getChat(id))
|
||||
)
|
||||
|
||||
const chatAuthors = await Promise.all(
|
||||
chats.map(chat => getUser(chat.author))
|
||||
)
|
||||
```
|
||||
|
||||
If one `getChat(id)` out of 100 is extremely slow, the authors of the other 99 chats can't start loading even though their data is ready.
|
||||
|
||||
**Correct (each item chains its own nested fetch):**
|
||||
|
||||
```tsx
|
||||
const chatAuthors = await Promise.all(
|
||||
chatIds.map(id => getChat(id).then(chat => getUser(chat.author)))
|
||||
)
|
||||
```
|
||||
|
||||
Each item independently chains `getChat` → `getUser`, so a slow chat doesn't block author fetches for the others.
|
||||
@@ -0,0 +1,38 @@
|
||||
---
|
||||
title: Minimize Serialization at RSC Boundaries
|
||||
impact: HIGH
|
||||
impactDescription: reduces data transfer size
|
||||
tags: server, rsc, serialization, props
|
||||
---
|
||||
|
||||
## Minimize Serialization at RSC Boundaries
|
||||
|
||||
The React Server/Client boundary serializes all object properties into strings and embeds them in the HTML response and subsequent RSC requests. This serialized data directly impacts page weight and load time, so **size matters a lot**. Only pass fields that the client actually uses.
|
||||
|
||||
**Incorrect (serializes all 50 fields):**
|
||||
|
||||
```tsx
|
||||
async function Page() {
|
||||
const user = await fetchUser() // 50 fields
|
||||
return <Profile user={user} />
|
||||
}
|
||||
|
||||
'use client'
|
||||
function Profile({ user }: { user: User }) {
|
||||
return <div>{user.name}</div> // uses 1 field
|
||||
}
|
||||
```
|
||||
|
||||
**Correct (serializes only 1 field):**
|
||||
|
||||
```tsx
|
||||
async function Page() {
|
||||
const user = await fetchUser()
|
||||
return <Profile name={user.name} />
|
||||
}
|
||||
|
||||
'use client'
|
||||
function Profile({ name }: { name: string }) {
|
||||
return <div>{name}</div>
|
||||
}
|
||||
```
|
||||
File diff suppressed because it is too large
Load Diff
@@ -0,0 +1,165 @@
|
||||
# React Native Guidelines
|
||||
|
||||
A structured repository for creating and maintaining React Native Best Practices
|
||||
optimized for agents and LLMs.
|
||||
|
||||
## Structure
|
||||
|
||||
- `rules/` - Individual rule files (one per rule)
|
||||
- `_sections.md` - Section metadata (titles, impacts, descriptions)
|
||||
- `_template.md` - Template for creating new rules
|
||||
- `area-description.md` - Individual rule files
|
||||
- `metadata.json` - Document metadata (version, organization, abstract)
|
||||
- **`AGENTS.md`** - Compiled output (generated)
|
||||
|
||||
## Rules
|
||||
|
||||
### Core Rendering (CRITICAL)
|
||||
|
||||
- `rendering-text-in-text-component.md` - Wrap strings in Text components
|
||||
- `rendering-no-falsy-and.md` - Avoid falsy && operator in JSX
|
||||
|
||||
### List Performance (HIGH)
|
||||
|
||||
- `list-performance-virtualize.md` - Use virtualized lists (LegendList,
|
||||
FlashList)
|
||||
- `list-performance-function-references.md` - Keep stable object references
|
||||
- `list-performance-callbacks.md` - Hoist callbacks to list root
|
||||
- `list-performance-inline-objects.md` - Avoid inline objects in renderItem
|
||||
- `list-performance-item-memo.md` - Pass primitives for memoization
|
||||
- `list-performance-item-expensive.md` - Keep list items lightweight
|
||||
- `list-performance-images.md` - Use compressed images in lists
|
||||
- `list-performance-item-types.md` - Use item types for heterogeneous lists
|
||||
|
||||
### Animation (HIGH)
|
||||
|
||||
- `animation-gpu-properties.md` - Animate transform/opacity instead of layout
|
||||
- `animation-gesture-detector-press.md` - Use GestureDetector for press
|
||||
animations
|
||||
- `animation-derived-value.md` - Prefer useDerivedValue over useAnimatedReaction
|
||||
|
||||
### Scroll Performance (HIGH)
|
||||
|
||||
- `scroll-position-no-state.md` - Never track scroll in useState
|
||||
|
||||
### Navigation (HIGH)
|
||||
|
||||
- `navigation-native-navigators.md` - Use native stack and native tabs
|
||||
|
||||
### React State (MEDIUM)
|
||||
|
||||
- `react-state-dispatcher.md` - Use functional setState updates
|
||||
- `react-state-fallback.md` - State should represent user intent only
|
||||
- `react-state-minimize.md` - Minimize state variables, derive values
|
||||
|
||||
### State Architecture (MEDIUM)
|
||||
|
||||
- `state-ground-truth.md` - State must represent ground truth
|
||||
|
||||
### React Compiler (MEDIUM)
|
||||
|
||||
- `react-compiler-destructure-functions.md` - Destructure functions early
|
||||
- `react-compiler-reanimated-shared-values.md` - Use .get()/.set() for shared
|
||||
values
|
||||
|
||||
### User Interface (MEDIUM)
|
||||
|
||||
- `ui-expo-image.md` - Use expo-image for optimized images
|
||||
- `ui-image-gallery.md` - Use Galeria for lightbox/galleries
|
||||
- `ui-menus.md` - Native dropdown and context menus with Zeego
|
||||
- `ui-native-modals.md` - Use native Modal with formSheet
|
||||
- `ui-pressable.md` - Use Pressable instead of TouchableOpacity
|
||||
- `ui-measure-views.md` - Measuring view dimensions
|
||||
- `ui-safe-area-scroll.md` - Use contentInsetAdjustmentBehavior
|
||||
- `ui-scrollview-content-inset.md` - Use contentInset for dynamic spacing
|
||||
- `ui-styling.md` - Modern styling patterns (gap, boxShadow, gradients)
|
||||
|
||||
### Design System (MEDIUM)
|
||||
|
||||
- `design-system-compound-components.md` - Use compound components
|
||||
|
||||
### Monorepo (LOW)
|
||||
|
||||
- `monorepo-native-deps-in-app.md` - Install native deps in app directory
|
||||
- `monorepo-single-dependency-versions.md` - Single dependency versions
|
||||
|
||||
### Third-Party Dependencies (LOW)
|
||||
|
||||
- `imports-design-system-folder.md` - Import from design system folder
|
||||
|
||||
### JavaScript (LOW)
|
||||
|
||||
- `js-hoist-intl.md` - Hoist Intl formatter creation
|
||||
|
||||
### Fonts (LOW)
|
||||
|
||||
- `fonts-config-plugin.md` - Load fonts natively at build time
|
||||
|
||||
## Creating a New Rule
|
||||
|
||||
1. Copy `rules/_template.md` to `rules/area-description.md`
|
||||
2. Choose the appropriate area prefix:
|
||||
- `rendering-` for Core Rendering
|
||||
- `list-performance-` for List Performance
|
||||
- `animation-` for Animation
|
||||
- `scroll-` for Scroll Performance
|
||||
- `navigation-` for Navigation
|
||||
- `react-state-` for React State
|
||||
- `state-` for State Architecture
|
||||
- `react-compiler-` for React Compiler
|
||||
- `ui-` for User Interface
|
||||
- `design-system-` for Design System
|
||||
- `monorepo-` for Monorepo
|
||||
- `imports-` for Third-Party Dependencies
|
||||
- `js-` for JavaScript
|
||||
- `fonts-` for Fonts
|
||||
3. Fill in the frontmatter and content
|
||||
4. Ensure you have clear examples with explanations
|
||||
|
||||
## Rule File Structure
|
||||
|
||||
Each rule file should follow this structure:
|
||||
|
||||
````markdown
|
||||
---
|
||||
title: Rule Title Here
|
||||
impact: MEDIUM
|
||||
impactDescription: Optional description
|
||||
tags: tag1, tag2, tag3
|
||||
---
|
||||
|
||||
## Rule Title Here
|
||||
|
||||
Brief explanation of the rule and why it matters.
|
||||
|
||||
**Incorrect (description of what's wrong):**
|
||||
|
||||
```tsx
|
||||
// Bad code example
|
||||
```
|
||||
````
|
||||
|
||||
**Correct (description of what's right):**
|
||||
|
||||
```tsx
|
||||
// Good code example
|
||||
```
|
||||
|
||||
Reference: [Link](https://example.com)
|
||||
|
||||
```
|
||||
|
||||
## File Naming Convention
|
||||
|
||||
- Files starting with `_` are special (excluded from build)
|
||||
- Rule files: `area-description.md` (e.g., `animation-gpu-properties.md`)
|
||||
- Section is automatically inferred from filename prefix
|
||||
- Rules are sorted alphabetically by title within each section
|
||||
|
||||
## Impact Levels
|
||||
|
||||
- `CRITICAL` - Highest priority, causes crashes or broken UI
|
||||
- `HIGH` - Significant performance improvements
|
||||
- `MEDIUM` - Moderate performance improvements
|
||||
- `LOW` - Incremental improvements
|
||||
```
|
||||
@@ -0,0 +1,121 @@
|
||||
---
|
||||
name: vercel-react-native-skills
|
||||
description:
|
||||
React Native and Expo best practices for building performant mobile apps. Use
|
||||
when building React Native components, optimizing list performance,
|
||||
implementing animations, or working with native modules. Triggers on tasks
|
||||
involving React Native, Expo, mobile performance, or native platform APIs.
|
||||
license: MIT
|
||||
metadata:
|
||||
author: vercel
|
||||
version: '1.0.0'
|
||||
---
|
||||
|
||||
# React Native Skills
|
||||
|
||||
Comprehensive best practices for React Native and Expo applications. Contains
|
||||
rules across multiple categories covering performance, animations, UI patterns,
|
||||
and platform-specific optimizations.
|
||||
|
||||
## When to Apply
|
||||
|
||||
Reference these guidelines when:
|
||||
|
||||
- Building React Native or Expo apps
|
||||
- Optimizing list and scroll performance
|
||||
- Implementing animations with Reanimated
|
||||
- Working with images and media
|
||||
- Configuring native modules or fonts
|
||||
- Structuring monorepo projects with native dependencies
|
||||
|
||||
## Rule Categories by Priority
|
||||
|
||||
| Priority | Category | Impact | Prefix |
|
||||
| -------- | ---------------- | -------- | -------------------- |
|
||||
| 1 | List Performance | CRITICAL | `list-performance-` |
|
||||
| 2 | Animation | HIGH | `animation-` |
|
||||
| 3 | Navigation | HIGH | `navigation-` |
|
||||
| 4 | UI Patterns | HIGH | `ui-` |
|
||||
| 5 | State Management | MEDIUM | `react-state-` |
|
||||
| 6 | Rendering | MEDIUM | `rendering-` |
|
||||
| 7 | Monorepo | MEDIUM | `monorepo-` |
|
||||
| 8 | Configuration | LOW | `fonts-`, `imports-` |
|
||||
|
||||
## Quick Reference
|
||||
|
||||
### 1. List Performance (CRITICAL)
|
||||
|
||||
- `list-performance-virtualize` - Use FlashList for large lists
|
||||
- `list-performance-item-memo` - Memoize list item components
|
||||
- `list-performance-callbacks` - Stabilize callback references
|
||||
- `list-performance-inline-objects` - Avoid inline style objects
|
||||
- `list-performance-function-references` - Extract functions outside render
|
||||
- `list-performance-images` - Optimize images in lists
|
||||
- `list-performance-item-expensive` - Move expensive work outside items
|
||||
- `list-performance-item-types` - Use item types for heterogeneous lists
|
||||
|
||||
### 2. Animation (HIGH)
|
||||
|
||||
- `animation-gpu-properties` - Animate only transform and opacity
|
||||
- `animation-derived-value` - Use useDerivedValue for computed animations
|
||||
- `animation-gesture-detector-press` - Use Gesture.Tap instead of Pressable
|
||||
|
||||
### 3. Navigation (HIGH)
|
||||
|
||||
- `navigation-native-navigators` - Use native stack and native tabs over JS navigators
|
||||
|
||||
### 4. UI Patterns (HIGH)
|
||||
|
||||
- `ui-expo-image` - Use expo-image for all images
|
||||
- `ui-image-gallery` - Use Galeria for image lightboxes
|
||||
- `ui-pressable` - Use Pressable over TouchableOpacity
|
||||
- `ui-safe-area-scroll` - Handle safe areas in ScrollViews
|
||||
- `ui-scrollview-content-inset` - Use contentInset for headers
|
||||
- `ui-menus` - Use native context menus
|
||||
- `ui-native-modals` - Use native modals when possible
|
||||
- `ui-measure-views` - Use onLayout, not measure()
|
||||
- `ui-styling` - Use StyleSheet.create or Nativewind
|
||||
|
||||
### 5. State Management (MEDIUM)
|
||||
|
||||
- `react-state-minimize` - Minimize state subscriptions
|
||||
- `react-state-dispatcher` - Use dispatcher pattern for callbacks
|
||||
- `react-state-fallback` - Show fallback on first render
|
||||
- `react-compiler-destructure-functions` - Destructure for React Compiler
|
||||
- `react-compiler-reanimated-shared-values` - Handle shared values with compiler
|
||||
|
||||
### 6. Rendering (MEDIUM)
|
||||
|
||||
- `rendering-text-in-text-component` - Wrap text in Text components
|
||||
- `rendering-no-falsy-and` - Avoid falsy && for conditional rendering
|
||||
|
||||
### 7. Monorepo (MEDIUM)
|
||||
|
||||
- `monorepo-native-deps-in-app` - Keep native dependencies in app package
|
||||
- `monorepo-single-dependency-versions` - Use single versions across packages
|
||||
|
||||
### 8. Configuration (LOW)
|
||||
|
||||
- `fonts-config-plugin` - Use config plugins for custom fonts
|
||||
- `imports-design-system-folder` - Organize design system imports
|
||||
- `js-hoist-intl` - Hoist Intl object creation
|
||||
|
||||
## How to Use
|
||||
|
||||
Read individual rule files for detailed explanations and code examples:
|
||||
|
||||
```
|
||||
rules/list-performance-virtualize.md
|
||||
rules/animation-gpu-properties.md
|
||||
```
|
||||
|
||||
Each rule file contains:
|
||||
|
||||
- Brief explanation of why it matters
|
||||
- Incorrect code example with explanation
|
||||
- Correct code example with explanation
|
||||
- Additional context and references
|
||||
|
||||
## Full Compiled Document
|
||||
|
||||
For the complete guide with all rules expanded: `AGENTS.md`
|
||||
@@ -0,0 +1,16 @@
|
||||
{
|
||||
"version": "1.0.0",
|
||||
"organization": "Engineering",
|
||||
"date": "January 2026",
|
||||
"abstract": "Comprehensive performance optimization guide for React Native applications, designed for AI agents and LLMs. Contains 35+ rules across 13 categories, prioritized by impact from critical (core rendering, list performance) to incremental (fonts, imports). Each rule includes detailed explanations, real-world examples comparing incorrect vs. correct implementations, and specific impact metrics to guide automated refactoring and code generation.",
|
||||
"references": [
|
||||
"https://react.dev",
|
||||
"https://reactnative.dev",
|
||||
"https://docs.swmansion.com/react-native-reanimated",
|
||||
"https://docs.swmansion.com/react-native-gesture-handler",
|
||||
"https://docs.expo.dev",
|
||||
"https://legendapp.com/open-source/legend-list",
|
||||
"https://github.com/nandorojo/galeria",
|
||||
"https://zeego.dev"
|
||||
]
|
||||
}
|
||||
@@ -0,0 +1,86 @@
|
||||
# Sections
|
||||
|
||||
This file defines all sections, their ordering, impact levels, and descriptions.
|
||||
The section ID (in parentheses) is the filename prefix used to group rules.
|
||||
|
||||
---
|
||||
|
||||
## 1. Core Rendering (rendering)
|
||||
|
||||
**Impact:** CRITICAL
|
||||
**Description:** Fundamental React Native rendering rules. Violations cause
|
||||
runtime crashes or broken UI.
|
||||
|
||||
## 2. List Performance (list-performance)
|
||||
|
||||
**Impact:** HIGH
|
||||
**Description:** Optimizing virtualized lists (FlatList, LegendList, FlashList)
|
||||
for smooth scrolling and fast updates.
|
||||
|
||||
## 3. Animation (animation)
|
||||
|
||||
**Impact:** HIGH
|
||||
**Description:** GPU-accelerated animations, Reanimated patterns, and avoiding
|
||||
render thrashing during gestures.
|
||||
|
||||
## 4. Scroll Performance (scroll)
|
||||
|
||||
**Impact:** HIGH
|
||||
**Description:** Tracking scroll position without causing render thrashing.
|
||||
|
||||
## 5. Navigation (navigation)
|
||||
|
||||
**Impact:** HIGH
|
||||
**Description:** Using native navigators for stack and tab navigation instead of
|
||||
JS-based alternatives.
|
||||
|
||||
## 6. React State (react-state)
|
||||
|
||||
**Impact:** MEDIUM
|
||||
**Description:** Patterns for managing React state to avoid stale closures and
|
||||
unnecessary re-renders.
|
||||
|
||||
## 7. State Architecture (state)
|
||||
|
||||
**Impact:** MEDIUM
|
||||
**Description:** Ground truth principles for state variables and derived values.
|
||||
|
||||
## 8. React Compiler (react-compiler)
|
||||
|
||||
**Impact:** MEDIUM
|
||||
**Description:** Compatibility patterns for React Compiler with React Native and
|
||||
Reanimated.
|
||||
|
||||
## 9. User Interface (ui)
|
||||
|
||||
**Impact:** MEDIUM
|
||||
**Description:** Native UI patterns for images, menus, modals, styling, and
|
||||
platform-consistent interfaces.
|
||||
|
||||
## 10. Design System (design-system)
|
||||
|
||||
**Impact:** MEDIUM
|
||||
**Description:** Architecture patterns for building maintainable component
|
||||
libraries.
|
||||
|
||||
## 11. Monorepo (monorepo)
|
||||
|
||||
**Impact:** LOW
|
||||
**Description:** Dependency management and native module configuration in
|
||||
monorepos.
|
||||
|
||||
## 12. Third-Party Dependencies (imports)
|
||||
|
||||
**Impact:** LOW
|
||||
**Description:** Wrapping and re-exporting third-party dependencies for
|
||||
maintainability.
|
||||
|
||||
## 13. JavaScript (js)
|
||||
|
||||
**Impact:** LOW
|
||||
**Description:** Micro-optimizations like hoisting expensive object creation.
|
||||
|
||||
## 14. Fonts (fonts)
|
||||
|
||||
**Impact:** LOW
|
||||
**Description:** Native font loading for improved performance.
|
||||
@@ -0,0 +1,28 @@
|
||||
---
|
||||
title: Rule Title Here
|
||||
impact: MEDIUM
|
||||
impactDescription: Optional description of impact (e.g., "20-50% improvement")
|
||||
tags: tag1, tag2
|
||||
---
|
||||
|
||||
## Rule Title Here
|
||||
|
||||
**Impact: MEDIUM (optional impact description)**
|
||||
|
||||
Brief explanation of the rule and why it matters. This should be clear and concise, explaining the performance implications.
|
||||
|
||||
**Incorrect (description of what's wrong):**
|
||||
|
||||
```typescript
|
||||
// Bad code example here
|
||||
const bad = example()
|
||||
```
|
||||
|
||||
**Correct (description of what's right):**
|
||||
|
||||
```typescript
|
||||
// Good code example here
|
||||
const good = example()
|
||||
```
|
||||
|
||||
Reference: [Link to documentation or resource](https://example.com)
|
||||
Some files were not shown because too many files have changed in this diff Show More
Reference in New Issue
Block a user