Subchapter 3.7

Advanced Event Handler Refs

rules/advanced-event-handler-refs.mdMarkdown1 KBView on GitHub

Store Event Handlers in Refs

Store callbacks in refs when used in effects that shouldn’t re-subscribe on callback changes.

Incorrect (re-subscribes on every render):

Advanced Event Handler Refs · Vercel React Best Practices · vercel-labs/agent-skills · Skills Docs

function useWindowEvent(event: string, handler: (e) => void) {
  useEffect(() => {
    window.addEventListener(event, handler)
    return () => window.removeEventListener(event, handler)
  }, [event, handler])
}

function useWindowEvent(event: string, handler: (e) => void) {
  const handlerRef = useRef(handler)
  useEffect(() => {
    handlerRef.current = handler
  }, [handler])

  useEffect(() => {
    const listener = (e) => handlerRef.current(e)
    window.addEventListener(event, listener)
    return () => window.removeEventListener(event, listener)
  }, [event])
}

import { useEffectEvent } from 'react'

function useWindowEvent(event: string, handler: (e) => void) {
  const onEvent = useEffectEvent(handler)

  useEffect(() => {
    window.addEventListener(event, onEvent)
    return () => window.removeEventListener(event, onEvent)
  }, [event])
}