一個封裝的Ajax類

// Ajax 封裝 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對象無法創(chuàng)建！請檢查IE安全設置！");}
}
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>連接未初始化.../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;imsg.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="正在獲取數(shù)據(jù)"; else title="正在獲取" + title;
        var msgbox = new messageDiv(title);
        x.onreadystatechange = function ()
        {
            if (async) switch (x.readystate) {
            case 1:
                msgbox.showmsg("正在初始化連接...");
                return;
            case 2:
                msgbox.showmsg("正在發(fā)送數(shù)據(jù)...");
                return;
            case 3:
                msgbox.showmsg("正在接收數(shù)據(jù)...");
                return;
            case 4:
                msgbox.showmsg("數(shù)據(jù)接收完成...");
                if (x.status == 200) {
                    cmd(x.responseText);
                    msgbox.clear();
                }
                else {
                    msgbox.showmsg("請求失敗," + x.statustext + "(" + x.status + ")");
                    setTimeout(msgbox.clear,3000);
                }
                return;
            }
        }
        x.open (method,url,async);
        if (method=="post") {msgbox.showmsg("正在接收數(shù)據(jù)...");x.send(postString);} else x.send();
        if (!async) {
            msgbox.showmsg("數(shù)據(jù)接收完成...");
            cmd(x.responseText);
            msgbox.clear();
        }
    }    
}