React useComponentWillUnmount hook

Executes a callback immediately before a component is unmounted and destroyed.

• Use the useEffect() hook with an empty array as the second argument. Return the provided callback to be executed only once before cleanup.
• Behaves like the componentWillUnmount() lifecycle method of class components.

const useComponentWillUnmount = onUnmountHandler => {
  React.useEffect(
    () => () => {
      onUnmountHandler();
    },
    []
  );
};

const Unmounter = () => {
  useComponentWillUnmount(() => console.log('Component will unmount'));

  return <div>Check the console!</div>;
};

ReactDOM.render(<Unmounter />, document.getElementById('root'));