获取layer.open弹出层的返回值

layer.open({
                    type: 2,
                    title: "设置围栏",
                    shadeClose: true,
                    shade: 0.4,
                    area: [‘90%‘, ‘90%‘],
                    content: "/ElectronicFence/Map?id=" + id + "&shapeType=" + shapeType,
                    btn: [‘确定‘,‘关闭‘],
                    yes: function(index){
                        //当点击‘确定’按钮的时候，获取弹出层返回的值
                        var res = window["layui-layer-iframe" + index].callbackdata();
                        //打印返回的值，看是否有我们想返回的值。
                        console.log(res);
                        //最后关闭弹出层
                        layer.close(index);
                    },
                    cancel: function(){
                        //右上角关闭回调
                    }
                });

<script>
 var callbackdata = function () {
            var data = {
                username: ‘zhangfj‘
            };
            return data;
        }
    </script>