Memory leak trong React component, cách phát hiện và fix?

Phát hiện: Chrome DevTools > Memory tab, check heap snapshots.

Nguyên nhân:

1. Quên cleanup subscriptions/timers trong useEffect.
2. Event listeners không remove.
3. Abort controller không cancel fetch

Fix: return cleanup function trong useEffect.

Pattern: const controller = new AbortController(); return () => controller.abort();

Detection: Chrome DevTools > Memory tab, compare heap snapshots.

Common causes:

1. Forgetting to clean up subscriptions/timers in useEffect.
2. Event listeners not removed.
3. Fetch not cancelled via AbortController

Fix: return a cleanup function from useEffect.

Pattern: const controller = new AbortController(); return () => controller.abort();