Function handleStart

04React/Day08/src/App.jsx:11–20

()

  const intrervalIdRef = useRef(null);

  function handleStart(){
    
    if(intrervalIdRef.current!=null){
      return;
    }

    intrervalIdRef.current = setInterval(()=>{
      setTime(time=>time+1);
    },1000);
  }

  function handleStop(){
    clearInterval(intrervalIdRef.current);