What is the useEffect cleanup function in React?

What is the useEffect cleanup function in React?

The useEffect cleanup function is a way to clean up side effects in React components. It runs when the component unmounts or before the effect runs again.

Can you give me an example of how to use it?

Sure! If you set up a subscription in useEffect, you can return a function that unsubscribes from it. Here's a simple example:

useEffect(() => {
  const subscription = someAPI.subscribe();
  return () => {
    subscription.unsubscribe();
  };
}, []);

What happens if I forget to include the cleanup function?

If you forget the cleanup function, you might end up with memory leaks or unwanted behavior, as the side effects may persist even after the component unmounts.

Are there any best practices for using cleanup functions?

Yes! Always clean up subscriptions, timers, or any external resources in the cleanup function to prevent memory leaks and ensure optimal performance.