VIP26/react/study4/project/src/components/Clock.jsx

import { useState, useEffect } from "react";
export default function Clock({ title = "北京时间" }) {
  let [now, setNow] = useState(new Date());
  useEffect(() => {
    let timer;
    timer = setInterval(() => {
      setNow(new Date());
    }, 1000);

    return ()=>{
        clearInterval(timer)
    };
  }, []);

  return (
    <div>
      <p>
        {title || "当前时间"}:{now.toLocaleString()}
      </p>
    </div>
  );
}