html5的跨域处理

这篇代码是我在一个技术博客中看到的，介绍的很细致。代码摘过来，自己可以常看看。
 1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 2 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
 3 <head>
 4     <meta http-equiv="Content-Type" content="text/html;charset=UTF-8" />
 5     <title>cross-domain demo by js8.in</title>
 6 </head>
 7 <body>
 8     <div style="100%;border:2px solid green;">
 9     
10         <h3>this page from :<span id="host"></span></h3>
11         <input type="text" value="" id="data" /><button id="btn" onclick="send();">提交</button>
12     
13     <div id="log">
14         <p><b>这里是收到的消息</b></p>
15     </div>
16     <iframe id="iframeA" src="http://4.qdemo.sinaapp.com/xdomain/postmessage/proxy.html" style="margin:10px;border:2px solid #ff6600;90%;height:400px;"></iframe>
17     </div>
18     <script type="text/javascript">
19         document.getElementById('host').innerHTML = location.host;
20         function send(){
21             var val = document.getElementById('data').value;
22             sendMessage(val);
23         }
24         (function(win, doc){
25             var ifr = doc.getElementById('iframeA').contentWindow;
26             var cb = function(json){
27                 var p = document.createElement('p');
28                 p.innerHTML = (new Date).toLocaleTimeString()+'收到消息：'+json;
29                 document.getElementById('log').appendChild(p);
30             };
31             var sendMessage = function(){
32                 if(win.postMessage){
33                     if (win.addEventListener) {
34                         win.addEventListener("message",function(e){
35                         cb.call(win,e.data);
36                     },false);
37                     }else if(win.attachEvent) {
38                         win.attachEvent("onmessage",function(e){
39                         cb.call(win,e.data);
40                     });
41                     }
42                     return function(data){
43                         ifr.postMessage(data,'*');
44                     };
45                 }else{
46                     var hash = '';
47                     
48                     setInterval(function(){
49                     
50                         if (win.name !== hash) {
51                             hash = win.name;
52                             cb.call(win, hash);
53                         }
54                     }, 50);
55                     return function(data){
56                         ifr.name = data;
57                     };
58                 }
59             };
60             win.sendMessage = sendMessage();
61         })(window, document);
62         
63     
64         
65     </script>
66 </body>
67 </html>
主要是其中的js部分，为了好理解，html我也拿过来了~~