创建XMLHttpRequest 对象

var XHRequest = false;
   /*@cc_on @*/
   /*@if (@_jscript_version >= 5)
   try
   {
    XHRequest = new ActiveXObject("Msxml2.XMLHTTP");
   }
   catch (e)
   {
    try
    {
     XHRequest = new ActiveXObject("Microsoft.XMLHTTP");
    }
    catch (e2)
    {
     XHRequest = false;
    }
   }
   @end @*/

   if (!XHRequest && typeof XMLHttpRequest != 'undefined')
   {
    XHRequest = new XMLHttpRequest();
    try
    {
     XHRequest = new XMLHttpRequest();
     if (http_request.overrideMimeType)
     {//设置MiME类别
      http_request.overrideMimeType("text/xml");
     }
    }
    catch (failed)
    {
     XHRequest = false;
    }
    if (!XHRequest)
     alert("初始化 XMLHttpRequest 失败!");
   }