计时器用法

一、setTimeout()和clearTimeout()一起使用，停止计时器。

 1 <!DOCTYPE HTML>
 2 <html>
 3 <head>
 4     <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
 5     <title>计时器</title>
 6 </head>
 7 <script type="text/javascript">
 8     var num=0,i;
 9     function startCount(){
10         document.getElementById('count').value=num;
11         num=num+1;
12         i=setTimeout("startCount()",1000);
13     }
14     function stopCount(){
15         clearTimeout(i);
16     }
17 </script>
18 </head>
19 <body>
20 <form>
21     <input type="text" id="count" />
22     <input type="button" value="Start" onclick="startCount()" />
23     <input type="button" value="Stop" onclick="stopCount()"  />
24 </form>
25 </body>
26 </html>
27

2、5秒后返回到首页

用的知识点:

<!DOCTYPE html>
<html>
 <head>
  <title>浏览器对象</title>  
  <meta http-equiv="Content-Type" content="text/html; charset=gb2312"/>   
 </head>
 <body>
  <H4>操作成功</H4>
  <p>
     <b id="second">5</b>秒后回到主页&nbsp;<a href="javascript:goBack();">返回</a>  
  </p>
 
<script type="text/javascript">  
 
    var sec = document.getElementById("second");
    var i = 5;
    var timer = setInterval(function(){
        i--;
        sec.innerHTML = i;
        if(i==1){
            window.location.href =  "http://www.imooc.com/";
        }
    },1000);
     
  function goBack(){ 
    window.history.go(-1);
  }  
  </script> 
 </body>
</html>