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Advanced Event Handler Refs

Source: .agents/references/coding-standard/vercel-react-best-practices/rules/advanced-event-handler-refs.md

Metadata​

  • title: Store Event Handlers in Refs
  • impact: LOW
  • impactDescription: stable subscriptions
  • tags: advanced, hooks, refs, event-handlers, optimization

Content​

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):

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

Correct (stable subscription):

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])
}

Alternative: use useEffectEvent if you're on latest React:

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])
}

useEffectEvent provides a cleaner API for the same pattern: it creates a stable function reference that always calls the latest version of the handler.