ajax请求加上loading遮罩

$.ajax({    url: "${ctx}/"+url,    data:{id:parm},    type:"POST",    beforeSend:function(){        index = layer.load(1, {            shade: [0.5,'#fff'] //0.1透明度的白色背景        });    },    complete: function () {        layer.close(index);    },    success:function(result) {        if(result.code==200){            parent.layer.alert(result.msg,function () {                parent.layer.closeAll();                location.reload();            });        }else{            layer.msg(result.msg);        }    }});