Ajax獲取XMLHttp對象的方法

function FactoryXMLHttpRequest() {
 if(window.XMLHttpRequest) {
 return new XMLHttpRequest();
 }else if(window.ActiveXObject) {
 var msxmls = new Array(
 'Msxml2.XMLHTTP.5.0',
 'Msxml2.XMLHTTP.4.0',
 'Msxml2.XMLHTTP.3.0',
 'Msxml2.XMLHTTP',
 'Microsoft.XMLHTTP');
 for (var i = 0; i < msxmls.length; i++) {
 try {
 return new ActiveXObject(msxmls[i]);
 } catch (e) {
 }
 }
 }
 throw new Error("Could not instantiate XMLHttpRequest");
}