AJAx 解析

function createXMLHttpRequest()
{
     if(window.XMLHttpRequest) {
     xmlHttp = new XMLHttpRequest();
    } else if(window.ActiveXObject) {
     var versions = ['Microsoft.XMLHTTP', 'MSXML.XMLHTTP', 'Microsoft.XMLHTTP', 'Msxml2.XMLHTTP.7.0', 'Msxml2.XMLHTTP.6.0', 'Msxml2.XMLHTTP.5.0', 'Msxml2.XMLHTTP.4.0', 'MSXML2.XMLHTTP.3.0', 'MSXML2.XMLHTTP'];
               for(var i=0; i<versions.length; i++) {
                try {xmlHttp = new ActiveXObject(versions[i]); }
                catch(e){}
              
             }
    }
}