优雅的ajax封转
封装：

var MonitorAjax = function() {this.XHR = function() {var xmlHttpRequest;if(window.XMLHttpRequest) {xmlHttpRequest = new XMLHttpRequest();} else if(window.ActiveXObject) {try {xmlHttpRequest = new ActiveXObject("Microsoft.XMLHTTP");} catch(e1) {try {xmlHttpRequest = new ActiveXObject("MSXML2.XMLHTTP");} catch(e2) {try {xmlHttpRequest = new ActiveXObject("MSXML3.XMLHTTP");} catch(e3) {alert('创建异步通信对象失败，这是因为浏览器不支持引起的');}}}} else {alert("貌似您的浏览器不支持异步通信，部分功能无法正常运行，请切换浏览器，如：IE浏览器");}return xmlHttpRequest;}();this.request = function(url,transferType,data,callbackFn) {this.XHR.open(transferType,url,true);this.XHR.onreadystatechange = function() {if(this.readyState == 4) {if(this.status == 200) {callbackFn(this.responseText);}}};if(transferType == "POST" || transferType == "post") {this.XHR.setRequestHeader("Content-Type","application/x-www-form-urlencoded;charset=UTF-8");}this.XHR.send(data);};}

调用：
var monitorAjax = new MonitorAjax();
monitorAjax.request("login.do","post","name=wangfeng",function(result) {
alert(result);
});