Javascript 计算节点js和mongodb中的订单总价

我用Node JS和MongoDB构建了一个订购系统，我想在服务器上计算订单

总价

，然后保存为新订单

let ref = (model) => {
  return { type: mongoose.Schema.Types.ObjectId, required: true, ref: model };
};

这是我的

订单

模型模式

{
  items: [
    {
      id: ref("menu_item"),
      count: String,
      size: String,
      options: [String],
    },
  ],
  total_price: String,
  tip: String,
};

{
  name: String,
  price: String,
  vat: String, // 3%
  size: [
    {
      name: String,
      unit: String,
      price: String,
      vat: String, // 3%
      in_stock: Boolean,
      is_default: Boolean,
    },
  ],
  options: [
    {
      title: String,
      options: [
        {
          name: String,
          price: String,
          vat: String, // 3%
          in_stock: Boolean,
          is_default: Boolean,
        },
      ],
    },
  ],
}

这是

菜单项

模型模式

{
  items: [
    {
      id: ref("menu_item"),
      count: String,
      size: String,
      options: [String],
    },
  ],
  total_price: String,
  tip: String,
};

{
  name: String,
  price: String,
  vat: String, // 3%
  size: [
    {
      name: String,
      unit: String,
      price: String,
      vat: String, // 3%
      in_stock: Boolean,
      is_default: Boolean,
    },
  ],
  options: [
    {
      title: String,
      options: [
        {
          name: String,
          price: String,
          vat: String, // 3%
          in_stock: Boolean,
          is_default: Boolean,
        },
      ],
    },
  ],
}

这怎么可能？ 这是我做的一些尝试，但这是错误的方式

当客户发送订单时，将调用此函数

async (req, res) => {
      let total = 0;
      let size_price = 0;
      let options_price = 0;
      
      let {
        items,
        tip,
      } = req.body;

      let price = 0;
      let item_price = items.forEach(async (el) => {
        let menu_item = await req.models.menu_item.findOne({ _id: el.id });
        price += parseInt(menu_item.price);
        console.log(menu_item.price) // first 12 second 9
        console.log(price) // first 12 second 21
      });
      

      console.log(price) // return 0
}

---

forEach

循环在执行下一次迭代/退出循环之前不会等待异步函数完成。为了等待数据库查询所有记录并更新

price

值，我们可以将所有承诺包装在

Promise.all

中，或者在

for of

循环中连续执行它们

以下是使用

Promise更新的代码。全部
：

async (req, res) => {
      let total = 0;
      let size_price = 0;
      let options_price = 0;
      
      let {
        items,
        tip,
      } = req.body;

      let price = 0;
      await Promise.all(items.map(async (el) => {
          let menu_item = await req.models.menu_item.findOne({ _id: el.id });
          price += parseInt(menu_item.price);
          console.log(menu_item.price) // first 12 second 9
          console.log(price) // first 12 second 21
        })
      );
      

      console.log(price) // return 0
}

forEach
循环在执行下一次迭代/退出循环之前不会等待异步函数完成。为了等待数据库查询所有记录并更新
price
值，我们可以将所有承诺包装在
Promise.all
中，或者在
for of
循环中连续执行它们

以下是使用
Promise更新的代码。全部
：

async (req, res) => {
      let total = 0;
      let size_price = 0;
      let options_price = 0;
      
      let {
        items,
        tip,
      } = req.body;

      let price = 0;
      await Promise.all(items.map(async (el) => {
          let menu_item = await req.models.menu_item.findOne({ _id: el.id });
          price += parseInt(menu_item.price);
          console.log(menu_item.price) // first 12 second 9
          console.log(price) // first 12 second 21
        })
      );
      

      console.log(price) // return 0
}