JavaScript实现动态显示登录时间与在线时长的方法

<html>
 <head>
 <title>online</title>
 <script language=javaScript>
 ///这里是获得登录时候的时间，用来和动态的时间做差来求时长
 var s = new Date();

 function clockon() {
 var thistime = new Date();
 //时间差
 diff = new Date();
 diff.setTime(Math.abs(thistime.getTime() - s.getTime()));
 timediff = diff.getTime();
 hos = Math.floor(timediff / (1000 * 60 * 60));
 mins = Math.floor(timediff / (1000 * 60));
 secs = Math.floor(timediff / 1000);
 //end
 var hours = thistime.getHours();
 var minutes = thistime.getMinutes();
 var seconds = thistime.getSeconds();

 if (eval(hours) < 10) {
  hours = "0" + hours;
 }
 if (eval(minutes) < 10) {
  minutes = "0" + minutes;
 }
 if (seconds < 10) {
  seconds = "0" + seconds;
 }
 thistime = hours + ":" + minutes + ":" + seconds;
 bgclockshade.innerHTML = thistime//这里动态的嵌入当前的时间
 //如果不取余的话，秒数是一直上升的，所以在达到一个60的时候就取余就可以解决这个问题了
 if (secs > 59) {
  secs = secs % 60;
 }
 if (mins > 59) {
  mins = mins % 60;
 }
 if (eval(secs) < 10) {
  secs = "0" + secs;
 }
 if (eval(mins) < 10) {
  mins = "0" + mins;
 }
 if (eval(hos) < 10) {
  hos = "0" + hos;
 }
 jishi.innerHTML = hos + ":" + mins + ":" + secs;
 var timer = setTimeout("clockon()", 200);
 }
</script>
 </head>
 <body onload="clockon();">
 登录时间：
 <div id="bgclockshade"></div>
 上网时长：
 <div id="jishi"></div>
 </body>
</html>