一个封装的Ajax类


            用法:  new Ajax().Request(url,cmd,async,method,postString,title)  参数:  url: 请求页面URL（必填）  cmd: 返回值处理函数（必填）  async: 是否异步 ,(ture|false), 默认true  method: 请求方式,(post|get), 默认get  postString: 请求方式为post时,请求内容  title: 请求内容标题  复制代码 代码如下:// Ajax 封装 2007-3-13 function createXMLHttpRequest() {     try {                     if (window.XMLHTTPRequest) {                     return new XMLHttpRequest();             }             else if (window.ActiveXObject) {                 return new ActiveXObject("Microsoft.XMLHTTP");             }         }         catch (e) {alert("XMLHttpRequest对象无法创建！请检查IE安全设置！");} } function messageDiv(t) {     var v = document.createElement("<div>");     v.innerHTML = "<table style=\"width:300px;\" id=message>" +                   "<tr style=\"font-size:12px;background-color:#EEEEff;color:#227933;height:20px\">" +                    "<td style=\"padding:2px;border-top:1px solid #E1E1E1;border-left:1px solid #E1E1E1;border-bottom:1px solid #818181;border-right:1px solid #A1A1A1\">" +                   "<nobr><img src=refresh.gif align=absmiddle> " + t + ",<span id=Span1>连接未初始化...</span></nobr></td></tr></table>";     var l = document.getElementsByName("message").length;     v.style.cssText = "position:absolute;bottom:" + (l*24) + "px;left:0px;display:none";     document.body.appendChild(v);     this.clear = function () {         document.body.removeChild(v);         var msg = document.getElementsByName("message");         for (var i=0;i<msg.length;i++){             msg[i].parentNode.style.cssText = "position:absolute;bottom:" + (i*24) + "px;left:0px";         }     }     this.showmsg = function (s) {         v.style.display = "";         v.all.Span1.innerHTML = s;     } } function Ajax() {     var x = new createXMLHttpRequest();     this.Request = function (url,cmd,async,method,postString,title) {         if (method!="post") method = "post"; else method = "get";         if (async!=true) async = true; else async = false;         if (typeof(postString)!="string") postString="";         if (typeof(title)!="string") title="正在获取数据"; else title="正在获取" + title;         var msgbox = new messageDiv(title);         x.onreadystatechange = function ()         {             if (async) switch (x.readystate) {             case 1:                 msgbox.showmsg("正在初始化连接...");                 return;             case 2:                 msgbox.showmsg("正在发送数据...");                 return;             case 3:                 msgbox.showmsg("正在接收数据...");                 return;             case 4:                 msgbox.showmsg("数据接收完成...");                 if (x.status == 200) {                     cmd(x.responseText);                     msgbox.clear();                 }                 else {                     msgbox.showmsg("请求失败," + x.statustext + "(" + x.status + ")");                     setTimeout(msgbox.clear,3000);                 }                 return;             }         }         x.open (method,url,async);         if (method=="post") {msgbox.showmsg("正在接收数据...");x.send(postString);} else x.send();         if (!async) {             msgbox.showmsg("数据接收完成...");             cmd(x.responseText);             msgbox.clear();         }     }     }