Performant timer js code for react comp

timer.js

import React from 'react';

const App = () => {
  const [timer, setTimer] = React.useState(0);
  const intervalRef = React.useRef<null | number>(null);

  function timer_handler() {
    setTimer(timer => timer + 1);
  }

  React.useEffect(() => {
    const intervalId = setInterval(timer_handler, 1000);
    intervalRef.current = intervalId;

    return () => clearInterval(intervalId);
  }, []);

  const handleStopTimer = () => {
    if (intervalRef.current) {
      clearInterval(intervalRef.current);
      intervalRef.current = null;
    } else {
      intervalRef.current = setInterval(timer_handler, 1000);
    }
  };

  return (
    <React.Fragment>
      <div>{timer}</div>
      <button onClick={handleStopTimer}>Stop timer</button>
    </React.Fragment>
  );
};

export default App;