/**
 * 發(fā)送ajax請求
 * @type {Object}
 * 使用方法如下:
 * $ajax.request(
 *     method: "post",            //請求方式
 *     url:    "index.php",       //請求的服務(wù)器地址
 *     data:   "name=itbsl&age=20",//請求時攜帶的參數(shù)
 *     dataType: "xml",           //期望服務(wù)器回應(yīng)的數(shù)據(jù)
 *     callback: function(res) {  //請求成功后的回調(diào)函數(shù)
 *         //處理數(shù)據(jù)
 *     }
 * );
 */
var $ajax = {
    request: function(obj) {

        //創(chuàng)建對象
        var xmlhttp;
        if(window.XMLHttpRequest) {
            //code for IE7+, Firefox, Chrome, Opera, Safari
            xmlhttp = new XMLHttpRequest();
        } else {
            //code for IE6, IE5
            xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
        }

        //建立連接
        if(obj.method == 'get') {
            xmlhttp.open(obj.method, obj.url+"?"+obj.data+"&"+Math.random(), true);
            xmlhttp.send();
        } if(obj.method == 'post') {
            xmlhttp.open(obj.method, obj.url, true);
            xmlhttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
            xmlhttp.send(obj.data);
        }

        //監(jiān)視請求的狀態(tài)
        xmlhttp.onreadystatechange = function () {
            if(xmlhttp.readyState == 4 && xmlhttp.status == 200) {
                if(obj.dataType == 'xml') {
                    obj.callback(xmlhttp.responseXML);
                } else if(obj.dataType == 'text') {
                    eval("var res = " + xmlhttp.responseText);
                    obj.callback(res);
                }
            }
        }
    }
}