案例：XML案例     状态：可编辑再运行    进入竖版
 运行结果　
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<button onclick="loadXMLDoc('/example/xdom/test_xmlhttp.txt')">Get Headers</button>
 
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<html>
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<head>
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<script type="text/javascript">
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var xmlhttp;
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function loadXMLDoc(url)
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{
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xmlhttp=null;
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if (window.XMLHttpRequest)
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  {// code for Firefox, Mozilla, IE7, etc.
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  xmlhttp=new XMLHttpRequest();
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  }
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else if (window.ActiveXObject)
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  {// code for IE6, IE5
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  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
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  }
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if (xmlhttp!=null)
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  {
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  xmlhttp.onreadystatechange=state_Change;
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  xmlhttp.open("GET",url,true);
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  xmlhttp.send(null);
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  }
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else
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  {
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  alert("Your browser does not support XMLHTTP.");
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  }
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}
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​
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function state_Change()
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{
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if (xmlhttp.readyState==4)
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  {// 4 = "loaded"
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  if (xmlhttp.status==200)
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    {// 200 = "OK"
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    document.getElementById('p1').innerHTML=xmlhttp.getAllResponseHeaders();
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    }
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  else
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    {
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    alert("Problem retrieving data:" + xmlhttp.statusText);
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    }
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  }
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}
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</script>
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</head>
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<body>
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​
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<p id="p1">
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The getAllResponseHeaders() function returns the headers of a resource.
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The headers contain file information like length,