以下为程序代码：
/*************************************************************************
        Ajax类
        Send方法的参数解释：
        Ajax.Send(Url[, Async[, CallFunc[, User[, Pass]]]]);
        Ajax：
                必选项，Ajax对象的一个实例。
        Url：
                必选项，请求的地址。
        Async：
                可选项，为空表示请求模式为GET，为具体参数（如：{key : "postkey", value : "postvalue"}）表示请求为POST。
        CallFunc：
                可选项，为空表示同步请求，为一个Function对象时表示异步请求并在Ajax的onreadystatechange事件中调用此函数。
        User：
                可选项，服务器需要验证时此参数为验证需要的用户名。
        Pass：
                可选项，服务器需要验证是此参数为验证需要的密码。
        例子：
        function getSend() {
                if(ajax.xml.readyState == 4 && ajax.xml.status == 200){
                        alert(ajax.xml.responseText);
                }
                else {
                        alert("wait...");
                }
        }
        var PostString = {
                classid : 1,
                search : "无忧脚本"
        }
        var ajax = new Ajax();
        ajax.Send("http://bbs.51js.com/");//GET同步请求，可用ajax.xml.responseText获取返回值
        ajax.Send("http://bbs.51js.com/", false, getSend);//GET异步请求，回调getSend()函数
        ajax.Send("http://bbs.51js.com/", PostString);//POST同步请求，可用ajax.xml.responseText获取返回值
        ajax.Send("http://bbs.51js.com/", PostString, getSend);//POST异步请求，回调getSend()函数
**************************************************************************/
function Ajax() {
        this.xmlObject = function() {
                try {
                        return new ActiveXObject("Microsoft.XMLHTTP");
                }
                catch(e) {
                        try {
                                return new ActiveXObject("Msxml2.XMLHTTP");
                        }
                        catch(e) {
                                try {
                                        return new XMLHttpRequest();
                                }
                                catch(e) {
                                        return window.createRequest();
                                } ;
                        };
                };
        };
        this.xml = this.xmlObject();
        this.Send = function() {
                var PostStr = !!arguments[1] ? (function() {
                        var tempArr = new Array();
                        for(var i in arguments.callee.caller.arguments[1]){
                                tempArr.push(i + "=" + arguments.callee.caller.arguments[1][i]);
                        }
                        return tempArr.join("&");
                })() : null;
                this.xml.open(PostStr ? "POST" : "GET", arguments[0], !!arguments[2], arguments[3], arguments[4]);
                !!arguments[2] ? this.xml.onreadystatechange = arguments[2] : null;
                if(PostStr){
                        this.xml.setRequestHeader("Content-Length", PostStr.length);
                        this.xml.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
                };
                this.xml.send(PostStr);
        };
};