JavaScript学习笔记-简单的计时钟表

 <!DOCTYPE html>

 <html lang="en" xmlns="http://www.w3.org/1999/xhtml">
 <head>
     <meta charset="utf-8" />
     <title>计时钟表</title>
     <script type="text/javascript">
         function startTime() {
             var today = new Date();     //实例化一个日期，创建一个日期对象，内容为当前时间
             var h = today.getHours();   //获取当前小时存入today
             var m = today.getMinutes(); //获取当前分钟存入today
             var s = today.getSeconds(); //获取当前秒存入today

             m = checkTime(m);    //给分钟不足2位的数十位上加个0
             s = checkTime(s);    //给秒数不足2位的数十位上加个0
             document.getElementById("txt").innerHTML = h + ":" + m + ":" + s;   //改变id为txt里的html为 小时：分钟：秒
             t = setTimeout(function () { startTime() }, 500);                   //在每隔500毫秒后调用startTime()这个方法
         };

         //给不足2位的数十位上加个0
         function checkTime(i) {
             if (i < 10) {
                 i = "0" + 1
             }return i;

         };

     </script>
 </head>
 <body onload="startTime()">
     <div id="txt"></div>
 </body>
 </html>