useRef_timer_id.js

function TimerWithRefID() {
  const setIntervalRef = useRef();

  useEffect(() => {
    const intervalID = setInterval(() => {
      // something to be done every 100ms
    }, 100);

    // this is where the interval ID is saved in the ref object 
    setIntervalRef.current = intervalID;
    return () => {
      clearInterval(setIntervalRef.current);
    };
  });
}