js获取url参数值，并解决中文乱码

<script type="text/javascript">
    function GetQueryString(name) {
        var reg = new RegExp("(^|&)" + name + "=([^&]*)(&|$)");
        var r = decodeURI(window.location.search).substr(1).match(reg);
        if (r != null){
            return unescape(r[2]); 
        }else{
            return null;
        }
    }
    
    //假设url地址是    http://www.xxx.com?userId=1&classId=10
    //弹窗显示userId的值        
    alert(GetQueryString("userId"));
    //弹窗显示classId的值
    alert(GetQueryString("classId"));
    
</script>