React useKeyPress hook

Listens for changes in the pressed state of a given key.

• Use the useState() hook to create a state variable that holds the pressed state of the given key.
• Define two handler functions that update the state variable on key down or key up accordingly.
• Use the useEffect() hook and EventTarget.addEventListener() to handle the 'keydown' and 'keyup' events.
• Use EventTarget.removeEventListener() to perform cleanup after the component is unmounted.

const useKeyPress = targetKey => {
  const [keyPressed, setKeyPressed] = React.useState(false);

  const downHandler = ({ key }) => {
    if (key === targetKey) setKeyPressed(true);
  };

  const upHandler = ({ key }) => {
    if (key === targetKey) setKeyPressed(false);
  };

  React.useEffect(() => {
    window.addEventListener('keydown', downHandler);
    window.addEventListener('keyup', upHandler);

    return () => {
      window.removeEventListener('keydown', downHandler);
      window.removeEventListener('keyup', upHandler);
    };
  }, []);

  return keyPressed;
};

const MyApp = () => {
  const wPressed = useKeyPress('w');

  return <p>The "w" key is {!wPressed ? 'not ' : ''}pressed!</p>;
};

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