var XMLHttp = {
    _objPool: [],

    _getInstance: function() {
        for (var i = 0; i < this._objPool.length; i++) {
            if (this._objPool[i].readyState == 0 || this._objPool[i].readyState == 4) {
                return this._objPool[i];
            }
        }

        // IE5中不支持push方法
        this._objPool[this._objPool.length] = this._createObj();

        return this._objPool[this._objPool.length - 1];
    },

    _createObj: function() {
        try {

            var objXMLHttp = new XMLHttpRequest();

        }

        catch (e) {

            try {

                var objXMLHttp = new ActiveXObject("Msxml2.XMLHTTP");
            }

            catch (e) {
                try {

                    var objXMLHttp = new ActiveXObject("Microsoft.XMLHTTP");
                }
                catch (e) {
                    return false;

                }

            }

        }

        // mozilla某些版本没有readyState属性
        if (objXMLHttp.readyState == null) {
            objXMLHttp.readyState = 0;

            objXMLHttp.addEventListener("load", function() {
                objXMLHttp.readyState = 4;

                if (typeof objXMLHttp.onreadystatechange == "function") {
                    objXMLHttp.onreadystatechange();
                }
            }, false);
        }

        return objXMLHttp;
    },

    // 发送请求(方法[post,get], 地址, 数据, 回调函数)
    sendReq: function(url, method, data, callback) {
        var objXMLHttp = this._getInstance();

        with (objXMLHttp) {
            try {
                // 加随机数防止缓存
                if (url.indexOf("?") > 0) {
                    url += "&randnum=" + Math.random();
                }
                else {
                    url += "?randnum=" + Math.random();
                }

                open(method, url, true);

                // 设定请求编码方式
                setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8');
                send(data);
                onreadystatechange = function() {
                    if (objXMLHttp.readyState == 4 && (objXMLHttp.status == 200 || objXMLHttp.status == 304)) {
                        callback(objXMLHttp);
                    }
                }
            }
            catch (e) {

            }
        }
    }
};


function CallBack(_objxmlhttp) {
    var _temp = eval("(" + _objxmlhttp.responseText + ")");
    for (i = 0; i < _temp.length; i++) {
        document.getElementById(_temp[i].key).innerHTML = _temp[i].value;
    }
}