[REACTJS] 후크와 반응에 카운트 다운 타이머를 구현

후크와 반응에 카운트 다운 타이머를 구현

해결법

1. ---

   1.

   const Timer = ({ seconds }) => {
     // initialize timeLeft with the seconds prop
     const [timeLeft, setTimeLeft] = useState(seconds);
   
     useEffect(() => {
       // exit early when we reach 0
       if (!timeLeft) return;
   
       // save intervalId to clear the interval when the
       // component re-renders
       const intervalId = setInterval(() => {
         setTimeLeft(timeLeft - 1);
       }, 1000);
   
       // clear interval on re-render to avoid memory leaks
       return () => clearInterval(intervalId);
       // add timeLeft as a dependency to re-rerun the effect
       // when we update it
     }, [timeLeft]);
   
     return (
       <div>
         <h1>{timeLeft}</h1>
       </div>
     );
   };
   

from https://stackoverflow.com/questions/57137094/implementing-a-countdown-timer-in-react-with-hooks by cc-by-sa and MIT license