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41 lines
1.0 KiB
Markdown
41 lines
1.0 KiB
Markdown
---
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title: Use Transitions for Non-Urgent Updates
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impact: MEDIUM
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impactDescription: maintains UI responsiveness
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tags: rerender, transitions, startTransition, performance
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---
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## Use Transitions for Non-Urgent Updates
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Mark frequent, non-urgent state updates as transitions to maintain UI responsiveness.
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**Incorrect (blocks UI on every scroll):**
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```tsx
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function ScrollTracker() {
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const [scrollY, setScrollY] = useState(0)
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useEffect(() => {
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const handler = () => setScrollY(window.scrollY)
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window.addEventListener('scroll', handler, { passive: true })
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return () => window.removeEventListener('scroll', handler)
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}, [])
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}
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```
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**Correct (non-blocking updates):**
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```tsx
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import { startTransition } from 'react'
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function ScrollTracker() {
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const [scrollY, setScrollY] = useState(0)
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useEffect(() => {
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const handler = () => {
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startTransition(() => setScrollY(window.scrollY))
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}
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window.addEventListener('scroll', handler, { passive: true })
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return () => window.removeEventListener('scroll', handler)
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}, [])
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}
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```
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