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## What does this PR do? This PR adds https://vercel.com/blog/introducing-react-best-practices for your coding agent using `npx add-skill vercel-labs/agent-skills` command The skills are added to `.claude/`, `.cursor/`, and `.opencode/` directories to provide React and Next.js performance optimization guidance for AI-assisted workflows. ## Updates since last revision Addressed Cubic AI review feedback for issues with confidence >= 9/10: - **rerender-dependencies.md** - Replaced `console.log(user.id)` with `fetchUserDetails(user.id)` to avoid logging sensitive information - **server-after-nonblocking.md** - Removed `sessionCookie` from `logUserAction` call to avoid logging sensitive authentication data, added `await` to async call - **bundle-conditional.md** - Added `loadError` state and `setLoadError` setter to fix undefined `setEnabled` reference - **advanced-event-handler-refs.md** - Updated `useWindowEvent` handler signature to accept `Event` parameter and forward it to the stored handler - **rerender-derived-state.md** - Closed `<nav>` elements in both examples for valid JSX Fixes applied to both `.claude` and `.cursor` skill directories for consistency. ## Mandatory Tasks (DO NOT REMOVE) - [x] I have self-reviewed the code (A decent size PR without self-review might be rejected). - [x] N/A I have updated the developer docs in /docs if this PR makes changes that would require a [documentation change](https://cal.com/docs). If N/A, write N/A here and check the checkbox. - [x] N/A, I confirm automated tests are in place that prove my fix is effective or that my feature works. ## How should this be tested? These are documentation files for AI coding agents. No runtime testing required - review the markdown files to verify the example code snippets are correct. ## Checklist for human review - [ ] Verify example code snippets in the skill files are syntactically correct - [ ] Confirm the fixes don't introduce new issues in the documentation examples - [ ] Check that `.claude` and `.cursor` directories have consistent content --- Link to Devin run: https://app.devin.ai/sessions/f7f7e67fdeea4b22a4817d63ed9e1759 Requested by: unknown ()
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title, impact, impactDescription, tags
| title | impact | impactDescription | tags |
|---|---|---|---|
| Use toSorted() Instead of sort() for Immutability | MEDIUM-HIGH | prevents mutation bugs in React state | 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):
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):
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:
- Props/state mutations break React's immutability model - React expects props and state to be treated as read-only
- 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:
// 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