Code
Object.extend =function(targetObj,fnJson){
    //扩展方法，类似于jQuery的$.extend,可以扩展类的方法，也可以合并对象
    for(var fnName in fnJson){
        targetObj[fnName]=fnJson[fnName];
    }
    return targetObj;
};

HttpAjax = (function(){
    function HttpAjax(options){
        var settings={
            type:‘post‘,        //请求类型
            url:‘‘,             //请求地址
            data:{"id":-1},     //json格式的参数
            success:function(){},//成功的回调函数
            failure:function(){},//失败的回调函数
            isAsyn:true           //是否为异步
        };
        this.options = Object.extend(settings,options);

        Object.extend(HttpAjax.prototype,{
            _createXhr:function(){
                if (typeof XMLHttpRequest !== ‘undefined‘) {
                    return new XMLHttpRequest();
                }
                else if (typeof ActiveXObject !== ‘undefined‘) {
                    var versions = [‘MSXML2.XMLHttp.6.0‘, ‘MSXML2.XMLHttp.3.0‘, ‘MSXML2.XMLHttp‘];
                    for (var i = 0, len = versions.length; i < len; i++) {
                        try {
                            var xhr = new ActiveXObject(versions[i]);
                            this.IsCreateOk = versions[i];
                            return xhr;
                        }
                        catch (e) { }
                    }
                    if (typeof this.IsCreateOk === ‘undefined‘) {
                        throw new Error("您的浏览器版本过低，无法创建异步对象，请升级您的浏览器！");
                    }
                }
            },
            _encodeData:function(paramters){
                var data = [];
                for (var name in paramters) {
                    //将数组中的数据以=拼接后再添加到data数组中 [name=aa,age=11]
                    var _regesp = /%20/g; //空格的正则表达式
                    var _value = paramters[name].toString(); //获取值
                    data.push(encodeURIComponent(name).replace(_regesp, ‘+‘) + "=" + encodeURIComponent(_value).replace(_regesp, ‘+‘));
                }
                //以&将数组元素拼接后返回 如：name=aa&age=11
                return data.join("&");
            },
            _regCallback:function(xhr){
                var _this=this;
                xhr.onreadystatechange = function(){
                    if (xhr.readyState == 4) {
                        if (xhr.status >= 200 && xhr.status < 300 || xhr.status == 300) {
                            _this.options.success(_this._getResponseData(xhr), xhr.statusText);
                        } else {
                            _this.options.failure(xhr.status, xhr.statusText);
                        }
                    }
                }
            },
            _getResponseData:function(xhr){
                var responseType = xhr.getResponseHeader("Content-Type");
                switch (responseType) {
                    case ‘text/xml‘:
                        return xhr.responseXML;
                    case ‘text/json‘:
                    case ‘text/javascript‘:
                    case ‘application/javascript‘:
                    case ‘application/x-javascript‘:
                        return eval(‘(‘ + xhr.responseText + ‘)‘);
                    default:
                        return xhr.responseText;
                };
            },
            _init:function(options){
                this.options=options;
                if(this.options.url=="") return;
                this.xhr = this._createXhr();//创建异步对象
                this._regCallback(this.xhr);//注册回调事件

                //根据请求类型，发送异步请求
                if(this.options.type.toLowerCase()=="post"){
                    this._post(this.xhr);
                }
                else{
                    this._get(this.xhr);
                }
            },
            _post:function(xhr){
                this.xhr=xhr;
                this.data=this._encodeData(this.options.data);
                this.url=this.options.url+"?d=" + parseInt(Math.random()*100+1,10);
                this.asyn=!!this.options.isAsyn;

                xhr.open("POST", this.url, this.asyn);
                xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
                xhr.send(this.data);
            },
            _get:function(xhr){
                this.xhr=xhr;
                this.data=this._encodeData(this.options.data);
                this.url=this.options.url+‘?‘ + this.data + ‘&d=‘ + parseInt(Math.random()*100+1,10);
                this.asyn=!!this.options.isAsyn;

                xhr.open(‘GET‘, this.url, this.asyn);
                xhr.send(null);
            }
        });
       this._init(this.options);
    };
    return HttpAjax;
})(window);