Missing Effect Cleanup (ARCH3302)

Key typescript.react.effect-cleanup · Severity warning · Category performance

React: flags an effect that starts a timer, listener or subscription without returning the matching teardown, leaking one handle per mount.

Incorrect

useEffect(() => {
  window.addEventListener("resize", onResize);
}, []);

Correct

useEffect(() => {
  window.addEventListener("resize", onResize);
  return () => window.removeEventListener("resize", onResize);
}, []);