如何判断js文件是否加载完成

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http://www.jquerycn.cn/a_11412

http://www.jizhuomi.com/software/535.html

1. function include_js(file) {    
2.       var _doc = document.getElementsByTagName('head')[0];     
3.       var js = document.createElement('script');     
4.       js.setAttribute('type', 'text/javascript');     
5.       js.setAttribute('src', file);     
6.       _doc.appendChild(js);     
7.       if (document.all) { //如果是IE     
8.             js.onreadystatechange = function () {     
9.                     if (js.readyState == 'loaded' || js.readyState == 'complete') {     
10.                       alert('IE6、IE7 support js.onreadystatechange');     
11.                   }     
12.            }     
13.       }     
14.       else {     
15.              js.onload = function () {     
16.                        alert('Firefox、chrome and others support js.onload');     
17.               }     
18.        }     
19. }    
20.      
21. include_js('jquery.js');  

面加载readyState的五种状态 
原文如下: 
0: (Uninitialized) the send( ) method has not yet been invoked. 
1: (Loading) the send( ) method has been invoked, request in progress. 
2: (Loaded) the send( ) method has completed, entire response received. 
3: (Interactive) the response is being parsed. 
4: (Completed) the response has been parsed, is ready for harvesting.

翻译成中文为: 
0 － （未初始化）还没有调用send()方法 
1 － （载入）已调用send()方法，正在发送请求 
2 － （载入完成）send()方法执行完成，已经接收到全部响应内容 
3 － （交互）正在解析响应内容 
4 － （完成）响应内容解析完成，可以在客户端调用了