Lifecycle

Summary

The stages a component goes through — mounting, updating, unmounting — and the hooks (`useEffect`) that let you run code at each stage in function components.

• 1Log messages in `useEffect` with different dependency arrays to see mount/update/unmount behavior.
• 2Compare lifecycle methods in class components to `useEffect` in function components.
• 3Learn the cleanup function returned from `useEffect` and when it runs.