layui多级弹框去掉遮罩

var index = layer.open({
    type:1,
    title:'请选择费用代码',
    area:['1050px','650px'],
    content:$('#selectFee'),
    btn:['确定','返回'],
    cancel:function () {},
    yes:function () {},
    btn2:function () {},
    success:function () {
        //多层弹窗只保留一层
        var mask = $(".layui-layer-shade");
        if(mask.length>=2){
            for(var i=1;i<mask.length;i++){
                $(mask[i]).remove()
            }
        }
    }
})