wehub-resource-sync
50 lines
1.2 KiB
Markdown
50 lines
1.2 KiB
Markdown
---
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title: useLatest for Stable Callback Refs
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impact: LOW
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impactDescription: prevents effect re-runs
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tags: advanced, hooks, useLatest, refs, optimization
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---
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## useLatest for Stable Callback Refs
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Access latest values in callbacks without adding them to dependency arrays. Prevents effect re-runs while avoiding stale closures.
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**Implementation:**
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```typescript
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function useLatest<T>(value: T) {
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const ref = useRef(value)
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useEffect(() => {
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ref.current = value
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}, [value])
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return ref
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}
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```
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**Incorrect (effect re-runs on every callback change):**
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```tsx
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function SearchInput({ onSearch }: { onSearch: (q: string) => void }) {
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const [query, setQuery] = useState('')
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useEffect(() => {
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const timeout = setTimeout(() => onSearch(query), 300)
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return () => clearTimeout(timeout)
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}, [query, onSearch])
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}
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```
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**Correct (stable effect, fresh callback):**
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```tsx
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function SearchInput({ onSearch }: { onSearch: (q: string) => void }) {
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const [query, setQuery] = useState('')
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const onSearchRef = useLatest(onSearch)
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useEffect(() => {
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const timeout = setTimeout(() => onSearchRef.current(query), 300)
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return () => clearTimeout(timeout)
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}, [query])
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}
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```
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