VUE的for循环

普通的for循环：

for (let i = 0; i < this.items.length; i++) {
    totalPrice += (this.items[i].price) * (this.items[i].count);
}

for in 循环，通过索引去拿到值

for (let i in this.items) {
    totalPrice += (this.items[i].price) * (this.items[i].count);
}

for of 循环，直接取到数组里面的对象

for (let item of this.items) {
    totalPrice += item.price * item.count;
}