Ajax创建XMLHttpRequest完整版

以下就是创建XMLHttpRequest完整版的代码，希望对大家有用~

function createXMLHttpRequest()
{
   if(window.ActiveXObject)
  {
    try {
                 xmlHttpRequest = new ActiveXObject("Msxml3.XMLHTTP");
        } catch (e) {
    try {
                 xmlHttpRequest = new ActiveXObject("Msxml2.XMLHTTP");
        } catch (e) {
   try {
                xmlHttpRequest = new ActiveXObject("Microsoft.XMLHTTP");
       } catch (e) {}}}
  }else if(window.XMLHttpRequest)
 {
          xmlHttpRequest=new XMLHttpRequest();
          if (xmlHttpRequest.overrideMimeType)
                  xmlHttpRequest.overrideMimeType('text/xml');
 }
}