跨域（五）——postMessage

HTML5的postMessage机制是客户端最直接的中档传输方法，一般用在iframe中父页与子页之间的客户端跨域通信。

浏览器支持情况：Chrome 2.0+、Internet Explorer 8.0+, Firefox 3.0+, Opera 9.6+, 和 Safari 4.0+ 。 Facebook已经使用了这个功能，用postMessage支持基于web的实时消息传递。

用法：otherWindow.postMessage(message, targetOrigin)

otherWindow: 对接收信息页面的window的引用。可以是页面中iframe的contentWindow属性；window.open的返回值；通过name或下标从window.frames取到的值。

message: 所要发送的数据，string类型。

targetOrigin: 用于限制otherWindow，“*”表示不作限制

下面是一个基于postMessage的简单聊天实例：

http://www.evil.com:8081/langtao/evil.html页面代码：

<iframe id="ifr" src="http://www.foo.com:8081/langtao/foo.html" width="500" height="300"></iframe>
<div id="msgbox">
</div>
<input type="text" id="msg" />
<input type="button" value="发送" id="btn"/>
<script type="text/javascript">
window.onload = function() {
    document.getElementById('btn').onclick=function(){
        var ifr = document.getElementById('ifr');
        var targetOrigin = 'http://www.foo.com:8081/langtao/';  // 若写成http://www.foo.com:8081/langtao/foo.html'效果一样
        var msg=document.getElementById('msg').value;
        ifr.contentWindow.postMessage(msg,targetOrigin);

        var c=document.createElement('div');
        c.innerHTML="你说："+msg;
        msgbox.appendChild(c);
    }
};
window.addEventListener('message', function(e){
    // 通过origin属性判断消息来源地址
    if (e.origin == 'http://www.foo.com:8081') {//不可以设置为'http://www.foo.com:8081/'
        var c=document.createElement('div');
        c.innerHTML="来自"+e.origin+"的消息："+e.data;
        msgbox.appendChild(c);
    }
}, false);
</script>

http://www.foo.com:8081/langtao/foo.html页面代码：

<div id="msgbox">
</div>
<input type="text" id="msg" />
<input type="button" value="发送" id="btn"/>
<script type="text/javascript">
    var msgbox=document.getElementById('msgbox');
    window.addEventListener('message', function(e){
        if (e.origin == 'http://www.evil.com:8081') {
            var c=document.createElement('div');
            c.innerHTML="来自"+e.origin+"的消息："+e.data;
            msgbox.appendChild(c);
        }
    }, false);
    document.getElementById('btn').onclick=function(){
        var targetOrigin = 'http://www.evil.com:8081/langtao/';
        var msg=document.getElementById('msg').value;
        window.top.postMessage(msg, targetOrigin);

        var c=document.createElement('div');
        c.innerHTML="你说："+msg;
        msgbox.appendChild(c);
    }
</script>

效果图：

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" alt="" />

从代码中可以看到，postMessage机制，这种跨域需要双方默契配合，且可以在客户端通过orgin进行判断请求的来源是否合法。