移动端的loading

<link rel="stylesheet" type="text/css" href="css/reset.css" />
        <link rel="stylesheet" type="text/css" href='layer-v3.1.1/layer/mobile/need/layer.css'>
js：
<script src="js/new_file.js"></script>
<script src="js/jquery-3.3.1.js"></script>
<script src="layer-v3.1.1/layer/mobile/layer.js"></script>
<script>

    $('#btn').click(function()
        $.ajax({
            dataType:'jsonp',
            type:'jsonp',
            url:'https://api.douban.com/v2/book/search?tag=%E7%AB%A5%E8%AF%9D&callback=',
            success:function(data){
                /*layer.open({
                    type:0,
                    content:'请求数据成功'
                })*/
                 layer.closeAll();
                 console.log(data);
                 console.log('我已经成功了');
                 console.log($(this));
                 $('#btn').attr('disabled','disabled');
            },
            beforeSend:function(){
                layer.open({
                    type:2,
                    content:'加载中'
                })
            },
            complete:function(){


            }

        });
    })