Node.js 聚合操作不返回任何具有mongoose模式的内容

其主要目的是获取对象的Orders数组的总价格.所以我使用了MongoDB聚合操作.我使用NoSQL Booster判断查询，在那里我可以得到totalPrice，但当我在应用程序中使用它时，它只有return me an empty array [].有谁能找出我漏掉了哪一点

**如下图所示.

 "userId": 1,
    "username": "john_doe",
    "password": "$2b$12$3fJyHTgM8QgU.q.tlpNVyOf.hJYfhVe7XPGCHm9Wq1RmexUZbUEeu",
    "fullName": {
        "firstName": "John",
        "lastName": "Doe"
    },
    "age": 30,
    "email": "john.doe@example.com",
    "isActive": true,
    "hobbies": [
        "reading",
        "traveling"
    ],
    "address": {
        "street": "123 Main St",
        "city": "Anytown",
        "country": "USA"
    },
    "orders": [
        {
            "productName": "Product 1",
            "price": 23.56,
            "quantity": 2
        },
        {
            "productName": "Product 2",
            "price": 23.56,
            "quantity": 5
        }
    ]

Below is the function pattern I used个

export const GetTotalOrderPriceDB = async (userId: string) => {
 const result = await User.aggregate([
  {
    $match: { userId: userId }, 
  },
  {
    $unwind: "$orders", 
  },
  {
    $group: {
      _id: null, 
      totalPrice: {
      $sum: { $multiply: ["$orders.price", "$orders.quantity"] },
      },
   },
 },
 {
  $project: {
    _id: 0,
    totalPrice: 1,
  },
 },
]);
return result;
};