c86c93582e
- Add 8 new skills (62 total, up from 58) - Official Anthropic skills: docx, pdf, pptx, xlsx, brand-guidelines, internal-comms - Vercel Labs skills: react-best-practices, web-design-guidelines - Implement dual-versioning: -official/-anthropic and -community suffixes - Update README with new skill registry and credits - Regenerate skills_index.json (62 skills validated) - Add comprehensive walkthrough.md BREAKING CHANGE: Document skills (docx/pdf/pptx/xlsx) renamed with version suffixes
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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