Udit TakkarandGitHub
7a9fdd5a0c
## 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 ()
83 lines
1.9 KiB
Markdown
83 lines
1.9 KiB
Markdown
---
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title: Batch DOM CSS Changes
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impact: MEDIUM
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impactDescription: reduces reflows/repaints
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tags: javascript, dom, css, performance, reflow
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---
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## Batch DOM CSS Changes
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Avoid changing styles one property at a time. Group multiple CSS changes together via classes or `cssText` to minimize browser reflows.
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**Incorrect (multiple reflows):**
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```typescript
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function updateElementStyles(element: HTMLElement) {
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// Each line triggers a reflow
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element.style.width = '100px'
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element.style.height = '200px'
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element.style.backgroundColor = 'blue'
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element.style.border = '1px solid black'
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}
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```
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**Correct (add class - single reflow):**
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```typescript
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// CSS file
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.highlighted-box {
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width: 100px;
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height: 200px;
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background-color: blue;
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border: 1px solid black;
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}
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// JavaScript
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function updateElementStyles(element: HTMLElement) {
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element.classList.add('highlighted-box')
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}
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```
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**Correct (change cssText - single reflow):**
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```typescript
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function updateElementStyles(element: HTMLElement) {
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element.style.cssText = `
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width: 100px;
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height: 200px;
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background-color: blue;
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border: 1px solid black;
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`
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}
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```
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**React example:**
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```tsx
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// Incorrect: changing styles one by one
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function Box({ isHighlighted }: { isHighlighted: boolean }) {
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const ref = useRef<HTMLDivElement>(null)
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useEffect(() => {
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if (ref.current && isHighlighted) {
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ref.current.style.width = '100px'
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ref.current.style.height = '200px'
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ref.current.style.backgroundColor = 'blue'
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}
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}, [isHighlighted])
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return <div ref={ref}>Content</div>
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}
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// Correct: toggle class
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function Box({ isHighlighted }: { isHighlighted: boolean }) {
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return (
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<div className={isHighlighted ? 'highlighted-box' : ''}>
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Content
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</div>
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)
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}
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```
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Prefer CSS classes over inline styles when possible. Classes are cached by the browser and provide better separation of concerns.
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