var $_GET = (function(){
            var url = window.document.location.href.toString();//获得当前url地址并转换成字符串
            var u = url.split("?");//以？来分割字符串，将？前后的值存到一个数组中
            if(typeof(u[1]) == "string"){//获得？后面具体的请求参数值
                u = u[1].split("&");
                var get = {};
                for(var i in u){
                    var j = u[i].split("=");
                    get[j[0]] = j[1];
                }
                return get;
            } else {
                return {};
            }
        })();