if ($ == undefined) {
    var $ = function(id) { return document.getElementById(id); }
}
function Ajax() {
    var _domId = null;
    var _xmlHttp = null;
    var _isAsynchronism = true;
    var _successFunction = null;
    this.createXMLHttpRequest = function() {
        try {
            if (window.ActiveXObject) {
                _xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
            } else {
                if (window.XMLHttpRequest) {
                    _xmlHttp = new XMLHttpRequest();
                } else {
                    _xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
                }
            }
        } catch (e) {
            alert(e.name + " : " + e.message);
        }
    };
    this.doPost = function(_url, _parameter) {
        try {
            _xmlHttp.open("POST", _url, _isAsynchronism);
            _xmlHttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
            _xmlHttp.send(_parameter);
        } catch (e) {
            alert(e.name + " : " + e.message);
        }
    };
    this.doGet = function(_url, _parameter) {
        try {
            var _random = Math.round(Math.random() * 10000);
            var _getParameter = (_url + "?random=" + _random + "&" + _parameter);
            if (_getParameter.length > 255) {
                this.doPost(_url, _parameter);
            } else {
                _xmlHttp.open("GET", _getParameter, _isAsynchronism);
                _xmlHttp.send(null);
            }
        } catch (e) {
            alert(e.name + " : " + e.message);
        }
    };
    this.backFunction = function() {
        if (_successFunction == null) {
            return;
        }
        if (_isAsynchronism) {
            if (_domId) {
                switch (_xmlHttp.readyState) {
                    case 1:
                        $(_domId).innerHTML = '<samp>正在建立连接.</smap>';
                        break;
                    case 2:
                        $(_domId).innerHTML = '<samp>正在发送数据.</smap>';
                        break;
                    case 3:
                        $(_domId).innerHTML = '<samp>正在接收数据.</smap>';
                        break;
                }
            }
            if ((_xmlHttp.readyState == 4) && (_xmlHttp.status == 200)) {
                _successFunction(_xmlHttp);
                return;
            }
        }
    };
    this.ajaxRequest = function(_id, _url, _parameter, _method, _asynchronism, _backFunction) {
        this.createXMLHttpRequest();
        _domId = _id;
        _isAsynchronism = _asynchronism;
        _successFunction = _backFunction;
        _xmlHttp.onreadystatechange = this.backFunction;
        if (_method.toLowerCase() == "post") {
            this.doPost(_url, _parameter);
        }
        else if (_method.toLowerCase() == "get") {
            this.doGet(_url, _parameter);
        }
    };
}