What is useEffect cleanup in React?

Can you explain what useEffect cleanup is in React?

Sure! In React, useEffect cleanup is a function that runs when a component unmounts or before the effect runs again.

Why is cleanup necessary in useEffect?

Cleanup is necessary to prevent memory leaks and to clean up subscriptions or timers that were set up in the effect.

Can you give me an example of useEffect with cleanup?

Of course! Here's a simple example: useEffect(() => { const timer = setTimeout(() => { console.log('Hello'); }, 1000); return () => clearTimeout(timer); }, []); This clears the timer when the component unmounts.

What happens if I forget to include cleanup?

If you forget cleanup, it can lead to memory leaks, as the timers or subscriptions may continue to run even after the component is unmounted.