秒表计时器的实现:
效果图如下:
用JS实现一个秒表计时器

附代码,已调试运行

<!DOCTYPE html> <html lang="en">  <head>     <meta charset="UTF-8">     <meta name="viewport" content="width=device-width, initial-scale=1.0">     <meta http-equiv="X-UA-Compatible" content="ie=edge">     <title>Document</title>     <style>         #div1 {             width: 300px;             height: 400px;             background: skyblue;             margin: 100px auto;             text-align: center;         }                  #count {             width: 200px;             height: 150px;             line-height: 150px;             margin: auto;             font-size: 40px;         }                  #div1 input {             width: 150px;             height: 40px;             background: orange;             font-size: 25px;             margin-top: 20px         }     </style> </head>  <body>     <div id="div1">         <div id="count">             <span id="id_H">00</span>             <span id="id_M">00</span>             <span id="id_S">00</span>         </div>         <input id="start" type="button" value="开始">         <input id="pause" type="button" value="暂停">         <input id="stop" type="button" value="停止">     </div>     <script>         //可以将查找标签节点的操作进行简化  var btn = getElementById('btn')         function $(id) {             return document.getElementById(id)         }         window.onload = function() {             //点击开始建 开始计数             var count = 0             var timer = null //timer变量记录定时器setInterval的返回值             $("start").onclick = function() {                 timer = setInterval(function() {                     count++;                     console.log(count)                         // 需要改变页面上时分秒的值                     console.log($("id_S"))                     $("id_S").innerHTML = showNum(count % 60)                     $("id_M").innerHTML = showNum(parseInt(count / 60) % 60)                     $("id_H").innerHTML = showNum(parseInt(count / 60 / 60))                 }, 1000)             }             $("pause").onclick = function() {                     //取消定时器                     clearInterval(timer)                 }                 //停止记数  数据清零  页面展示数据清零             $("stop").onclick = function() {                 //取消定时器                 $("pause").onclick()                     // clearInterval(timer)                     //数据清零  总秒数清零                 count = 0                     //页面展示数据清零                 $("id_S").innerHTML = "00"                 $("id_M").innerHTML = "00"                 $("id_H").innerHTML = "00"             }              //封装一个处理单位数字的函数             function showNum(num) {                 if (num < 10) {                     return '0' + num                 }                 return num             }         }     </script> </body>  </html>