AJax 源码思路

 1 function ajax(url , fnSucc , fnFaild )
 2 {
 3     //创建一个ajax
 4     var oAjax = null;
 5     if(window.XMLHttpRequest)
 6     {
 7         oAjax = new XMLHttpRequest;
 8     }
 9     else
10     {
11         oAjax = new ActiveXObject(‘Microsoft.XMLHTTP‘);
12     }
13 
14     //创建连接
15     oAjax.open(‘GET‘, url , true);
16 
17     //发送请求
18     oAjax.send();
19 
20     //返回数据
21     oAjax.onreadystatechange=function()
22     {
23         if(oAjax.readyState == 4)
24         {
25             if(oAjax.status == 200)
26             {
27                 fnSucc(oAjax.responseText);
28             }
29             else
30             {
31                 if(fnFaild)//如果有第三个参数 才执行
32                 {
33                     fnSucc();
34                 }
35 
36             }
37         }
38     }
39 }