| 1 | --- |
| 2 | title: Use Transitions for Non-Urgent Updates |
| 3 | impact: MEDIUM |
| 4 | impactDescription: maintains UI responsiveness |
| 5 | tags: rerender, transitions, startTransition, performance |
| 6 | --- |
| 7 | |
| 8 | ## Use Transitions for Non-Urgent Updates |
| 9 | |
| 10 | Mark frequent, non-urgent state updates as transitions to maintain UI responsiveness. |
| 11 | |
| 12 | **Incorrect (blocks UI on every scroll):** |
| 13 | |
| 14 | ```tsx |
| 15 | function ScrollTracker() { |
| 16 | const [scrollY, setScrollY] = useState(0) |
| 17 | useEffect(() => { |
| 18 | const handler = () => setScrollY(window.scrollY) |
| 19 | window.addEventListener('scroll', handler, { passive: true }) |
| 20 | return () => window.removeEventListener('scroll', handler) |
| 21 | }, []) |
| 22 | } |
| 23 | ``` |
| 24 | |
| 25 | **Correct (non-blocking updates):** |
| 26 | |
| 27 | ```tsx |
| 28 | import { startTransition } from 'react' |
| 29 | |
| 30 | function ScrollTracker() { |
| 31 | const [scrollY, setScrollY] = useState(0) |
| 32 | useEffect(() => { |
| 33 | const handler = () => { |
| 34 | startTransition(() => setScrollY(window.scrollY)) |
| 35 | } |
| 36 | window.addEventListener('scroll', handler, { passive: true }) |
| 37 | return () => window.removeEventListener('scroll', handler) |
| 38 | }, []) |
| 39 | } |
| 40 | ``` |
| 41 |