自定义组件：

仅在
IE8下组件内的属性无法读取（如CsShowBG ）

ko.components.register('couponselect', {
   viewModel: function (params) {
     var _this = this;

    _this.CsShowBG = ko.observable(params.IsOpen());
    _this.ShowSelectCouponDialog = ko.observable(params.IsOpen());
    _this.DealerCouponList = ko.observableArray();
    _this.CheckedCouponIds = ko.observableArray();
    _this.CheckedCouponId = ko.observable("");
    _this.CloseCouponSelDialog = function () {
        if (params.IsOpen) {
            params.IsOpen(false);
        }
    }
    _this.GoToCoupon = function () {
        var url = params.CouponManageURL.replace("&", "&");
        window.open(url);
    }
    //打开优惠券选择框
    _this.OpenCouponDialog = function () {

        _this.ShowSelectCouponDialog(true);
        _this.ShowBG(true)
    }

报错如下

有人遇到过吗？跪求解决方案