可以直接看下效果

代码：

 <script>



        let list = [
            {
                num: 1,
                price: 10,
            },
            {
                num: 2,
                price: 10,
            },
            {
                num: 3,
                price: 10,
            },
            {
                num: 4,
                price: 10,
            },
        ]
     // for循环 求总数和 num的和
        let num = 0
        for (let i = 0; i < list.length; i++) {
            num += list[i].num
        }
        console.log('第一种：' + num);

     // forEach 循环 num的和
        let number = 0
        list.forEach(v => {
            number += v.num
        });
        console.log('第二种：' + number);

     // reduce方法
        let sum
        sum = list.reduce((sum, obj) => (sum += obj.num), 0)
        console.log('第三种：' + sum);
    </script>




// 也可以直接封装一个方法 ，获取总量和总钱数 
<script>

 // 总价及数量
  const totalData = function (data) {
    const priceInfoObj = {};

    priceInfoObj.totalNumber = data.reduce(
      (totalNumber, obj) => (totalNumber += obj.num),
      0,
    );
    priceInfoObj.priceSum = data.reduce(
      (priceSum, obj) => (priceSum += obj.price * obj.num),
      0,
    );
    return priceInfoObj
  };


console.log(totalData(list))


</script>