实现场景

1. 倒数计时

const countdown = (seconds) => {
  if (seconds < 0) return;
  setTimeout(() => {
    countdown(seconds - 1);
  }, 1000);
};

countdown(10);

const countdown = (seconds) => {
  setInterval(() => {
    seconds--;
    if (seconds < 0) return;
    console.log(seconds);
  }, 1000);
};

2.实现倒计时 hooks

const useCountdown = (seconds) => {
  const [count, setCount] = useState(seconds);
  useEffect(() => {
    if (count <= 0) return;
    const timer = setTimeout(() => {
      setCount(count - 1);
    }, 1000);
    return () => {
      clearTimeout(timer);
    };
  }, [count]);
  return count;
};

// 调用
const countdown = useCountdown(10);