famapp/.agents/skills/react-best-practices/rules/advanced-event-handler-refs.md

title, impact, impactDescription, tags

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

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.