JS实现购物车中商品总价计算

<script type="text/javascript">
 // 总价变量
 var sum = 0;
 // 商品对象
 function Goods(name,price,amount){
 this.name = name;
 this.price = price;
 this.amount = amount;
 // this.add = fun();
  }
 // 定义声明商品实例
 var goods1 = new Goods("钢笔",100,1);
 var goods2 = new Goods("纸巾",10,1);
 var goods3 = new Goods("练习册",100,2);
  
 // 创建函数进行总价计算
 function totalPrice(){
 // 将对象放入数组
 var arr = new Array(goods1,goods2,goods3);
 // 通过遍历将各个商品价格进行相加
 for(var i in arr){
  sum = sum + (arr[i].price * arr[i].amount);
  };
  console.log(sum);
 };
  
 console.log(goods1);
 console.log(goods2);
 console.log(goods3);
 totalPrice();
</script>