this.shopCart是接口拿到的購(gòu)物車對(duì)象 遍歷對(duì)象中的num

 goodsNum() {
                let num = 0;
                Object.values(this.shopCart).forEach((goods, index) => {
                    num += Number(goods.num);
                });
                if (num > 0) {
                    return num;
                }
            },