/react-best-practices

useEffectEvent for Stable Callback Refs

Access latest values in callbacks without adding them to dependency arrays. Prevents effect re-runs while avoiding stale closures.

Incorrect (effect re-runs on every callback change):

function SearchInput({ onSearch }: { onSearch: (q: string) => void }) {
  const [query, setQuery] = useState('')

  useEffect(() => {
    const timeout = setTimeout(() => onSearch(query), 300)
    return () => clearTimeout(timeout)
  }, [query, onSearch])
}

Correct (using React's useEffectEvent):

import { useEffectEvent } from 'react';

function SearchInput({ onSearch }: { onSearch: (q: string) => void }) {
  const [query, setQuery] = useState('')
  const onSearchEvent = useEffectEvent(onSearch)

  useEffect(() => {
    const timeout = setTimeout(() => onSearchEvent(query), 300)
    return () => clearTimeout(timeout)
  }, [query])
}