LayUI的iframe窗口关闭后传值至父页面

layer.open({
            type: 2,
            title: "指标选择",
            closeBtn: 1, //显示关闭按钮
            area: ['400px', '215px'],
            content: ['/system/target', 'no'], //iframe的url，no代表不显示滚动条
            btn: ['确定','关闭'],
            yes: function(index){
                //获取子页面的返回值
                var iframeWin = window["layui-layer-iframe" + index];
                var res = iframeWin.callbackdata();
                console.log(res.target);
                //关闭子页面
                layer.close(index);
            }
        })

var target = "";

//返回父页面参数
var callbackdata = function () {
    var data = {
        "target":target
    };
    return data;
}