TypeScript

Type Parameters that Extend Document扩展文档的类型参数

The following classes accept all types that extend the Document interface:以下类接受扩展Document接口的所有类型：

• Collection
• ChangeStream

You can pass a type parameter that extends the Document interface like this:您可以传递一个扩展Document接口的类型参数，如下所示：

interface Pet {
  name: string;
  age: number;
}

const database = client.db("<your database>");
const collection = database.collection<Pet>("<your collection>");

interface User {
  email: string;
}

const database = client.db("<your database>");
const myColl = db.collection<User>("<your collection>");
myColl.find({ age: "Accepts any type!" });

Type Parameters of Any Type任何类型的类型参数

The following classes accept all type parameters:以下类接受所有类型参数：

• FindCursor
• AggregationCursor

You can find a code snippet that shows how to specify a type for the FindCursor class in the Find Multiple Documents Usage Example.您可以在查找多个文档用法示例中找到一个代码片段，该代码片段显示如何为FindCursor类指定类型。

Type Safety and Dot Notation类型安全和点符号

Starting in version 5.0, by default, the Node.js driver does not provide type safety for operations that search on fields expressed in dot notation. 默认情况下，从版本5.0开始，Node.js驱动程序不会为搜索以句点表示的字段的操作提供类型安全性。Dot notation is a syntax you can use to navigate nested JSON objects. When you construct a filter to pass to a query, the driver will not raise a type error even if you specify an incorrectly typed value for a field expressed in dot notation.点表示法是一种可以用于导航嵌套JSON对象的语法。当您构造要传递给查询的筛选器时，即使您为以句点表示的字段指定了类型不正确的值，驱动程序也不会引发类型错误。

The following code snippet defines the ClassificationPet interface, which includes a classification field that enables you to specify the genus and color of dogs and cats:以下代码片段定义了ClassificationPet界面，其中包括一个classification字段，用于指定狗和猫的属和颜色：

interface ClassificationPet {
  name: string;
  age: number;
  classification: { genus: "Canis" | "Felis"; color: string };
}

The driver does not raise a type error for the following code sample, even though the value of classification.color is a boolean instead of a string:驱动程序不会引发以下代码示例的类型错误，即使classification.color的值是布尔值而不是字符串：

await myColl.findOneAndDelete({ "classification.color": false });

You can enable type-checking by constructing filters as StrictFilter or StrictUpdateFilter types.您可以通过将筛选器构造为StrictFilter或StrictUpdateFilter类型来启用类型检查。

In the following code sample, the filter is assigned a StrictFilter type. 在下面的代码示例中，为筛选器分配了StrictFilter类型。Given this filter type, the Node.js driver reports a type error because the value of classification.color is a boolean instead of a string.给定这个筛选器类型，Node.js驱动程序会报告一个类型错误，因为classification.color的值是布尔值而不是字符串。

const filterPredicate: StrictFilter<ClassificationPet> = { "classification.color": false };
await myColl.findOneAndDelete(filterPredicate);

The following example assigns a StrictUpdateFilter type to an update filter. 以下示例将StrictUpdateFilter类型分配给更新筛选器。The Node.js driver reports a type error because the value of classification.color is a boolean instead of a string.Node.js驱动程序报告了一个类型错误，因为classification.color的值是布尔值而不是字符串。

const updateFilter: StrictUpdateFilter<ClassificationPet> = { $set: { "classification.color": false } }
await pets.updateOne({}, updateFilter);

interface ClassificationPet {
  name: string;
  mealtimes: Mealtime[];
}

interface Mealtime{
  time: string;
  amount: number;
}

const mealCounter = 1;

await myColl.findOneAndUpdate(
  { name: "Lassie" },
  { $set: { [`mealtimes.${mealCounter}.time` as const]: '4:00 PM' } },
);

Insert Operations and the _id Field插入操作和_id字段

How you specify the _id field in type parameters passed to your Collection instance affects the behavior of insert operations. 在传递给Collection实例的类型参数中指定_id字段的方式会影响插入操作的行为。The following table describes how different _id field specifications affect insert operations:下表描述了不同的_id字段规范如何影响插入操作：

If you must specify the _id field as required in the type you define to represent documents in your collection but you do not want to specify values for the _id field in insert operations, use the OptionalId helper type when you create your collection. 如果必须根据需要在定义的类型中指定_id字段以表示集合中的文档，但不希望在插入操作中为_id字段指定值，请在创建集合时使用OptionalId帮助器类型。The OptionalId type accepts a type parameter as an argument and returns that type with an optional _id field.OptionalId类型接受一个类型参数作为参数，并使用可选的_id字段返回该类型。

The following code snippet defines the IdPet interface, which includes a type for the _id field:以下代码片段定义了IdPet接口，其中包括_id字段的类型：

interface IdPet {
  _id: ObjectId;
  name: string;
  age: number;
}

The following code uses the preceding interface along with the OptionalId type to insert a document without specifying a value for the _id field:以下代码使用前面的接口和OptionalId类型插入文档，而不指定_id字段的值：

const database = client.db("<your database>");
const collection = db.collection<OptionalId<IdPet>>("<your collection>");

myColl.insertOne({
  name: "Spot",
  age: 2
});

To learn more about the _id field, see The _id Field in the MongoDB manual.要了解有关_id字段的更多信息，请参阅MongoDB手册中的_id字段。

To learn more about the types, interfaces, and classes discussed in this section, see the following resources:要了解本节中讨论的类型、接口和类的更多信息，请参阅以下资源：

• OptionalId API documentationAPI文件
• PkFactory API documentationAPI文件
• ObjectId source code源代码

Find Methods and the _id Field查找方法和_id字段

The find and findOne methods of the Collection class include the _id field in their return type. Collection类的find和findOne方法在其返回类型中包含_id字段。The driver infers the type of the returned _id field based on the type parameter you passed to your Collection instance.驱动程序根据传递给Collection实例的类型参数推断返回的_id字段的类型。

If the type parameter you passed to your Collection instance includes the _id field in its schema, the driver infers that the _id field returned from the method is of the type specified in the schema.如果传递给Collection实例的类型参数在其架构中包含_id字段，则驱动程序推断从方法返回的_id字段属于架构中指定的类型。

However, if the type parameter you passed to your Collection instance does not include the _id field in its schema, the driver infers that the type of the _id field returned from the method is ObjectId.但是，如果传递给Collection实例的类型参数在其架构中不包括_id字段，则驱动程序推断从该方法返回的_id字段的类型为ObjectId。

The following code uses the Pet interface to return a document with an _id inferred to be of type ObjectId:以下代码使用Pet接口返回一个_id被推断为ObjectId类型的文档：

const database = client.db("<your database>");
const collection = db.collection<Pet>("<your collection>");

const document = await myColl.findOne({
  name: "Spot",
});
const id : ObjectId = document._id;

The following code uses the IdNumberPet interface to return a document with an _id inferred to be of type number:以下代码使用IdNumberPet接口返回一个_id被推断为number类型的文档：

interface IdNumberPet {
  _id: number;
  name: string;
  age: number;
}

const database = client.db("<your database>");
const collection = db.collection<IdNumberPet>("<your collection>");

const document = await myColl.findOne({
  name: "Spot",
});
const id : number = document._id;

const doc = await myColl.findOne(
  {},
  { projection: { _id: 0, name: 1 } }
);
console.log(doc._id.generationTime);

interface ProjectedDocument {
   name: string
}

const doc = await myColl.findOne<ProjectedDocument>(
  {},
  { projection: { _id: 0, name: 1 } }
);
// Compile time error: Property '_id' does not exist on type 'ProjectedDocument'.
console.log(doc._id.generationTime);