js实现倒计时原生js实现倒计时，开箱即用，各位同学可根据业务需求做更改。如有错漏，恳请大佬们指正.[抱拳] 学如逆水行

不废话，上图，上代码.

<body>
  <input type="text" id="timetext" value="00时00分00秒" readonly><br>
  <button type="button" onclick="start()">开始</button>
  <button type="button" onclick="stop()">暂停</button>
  <button type="button" onclick="Reset()">重置</button>
 </body>

 <script>
    var hour = 0;
    var minute = 0;
    var second = 0 ;
    var millisecond = 0;
    var int;
    
    function Reset() {
      window.clearInterval(int);
      millisecond = hour = minute = second = 0;
      document.getElementById('timetext').value = '00时00分00秒000毫秒';
    }

    function start() {
      int = setInterval(timer, 50);
    }

    function timer() {
      millisecond = millisecond + 50;
      if (millisecond >= 1000) {
        millisecond = 0;
        second = second + 1;
      }
      if (second >= 60) {
        second = 0;
        minute = minute + 1;
      }
      if (minute >= 60) {
        minute = 0;
        hour = hour + 1;
      }
      document.getElementById('timetext').value = hour + '时' + minute + '分' + second + '秒' + millisecond + '毫秒';
    }

    function stop() {
      window.clearInterval(int);
    }
  </script>