Database Manual / Reference / mongosh Methods / Cursors

cursor.map() (mongosh method方法)

cursor.map(function)

Important

mongosh Method方法

This page documents a mongosh method. This is not the documentation for a language-specific driver, such as Node.js.本页记录了一种mongosh方法。这不是针对特定语言驱动程序（如Node.js）的文档。

For MongoDB API drivers, refer to the language-specific MongoDB driver documentation.有关MongoDB API驱动程序，请参阅特定语言的MongoDB驱动程序文档。

Applies a function to each document visited by the cursor and collects the return values from successive applications of the function into a Cursor object.将function应用于游标访问的每个文档，并将函数连续应用程序的返回值集合到游标对象中。

The cursor.map() method has the following parameter:cursor.map()方法有以下参数：

Parameter参数Type类型Description描述
functionfunctionA function to apply to each document visited by the cursor.应用于游标访问的每个文档的函数。

Compatibility兼容性

This method is available in deployments hosted in the following environments:此方法在以下环境中托管的部署中可用：

  • MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud：云中MongoDB部署的完全托管服务

Note

This command is supported in all MongoDB Atlas clusters. 所有MongoDB Atlas集群都支持此命令。For information on Atlas support for all commands, see Unsupported Commands.有关Atlas支持所有命令的信息，请参阅不支持的命令。

  • MongoDB Enterprise: The subscription-based, self-managed version of MongoDB：MongoDB的基于订阅的自我管理版本
  • MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB：MongoDB的源代码可用、免费使用和自我管理版本

Behavior行为

cursor.map() returns a Cursor object. 返回一个Cursor对象。Note that .map() only converts the type, it does not create a new cursor. 请注意，.map()只转换类型，它不会创建新的游标。You can convert the Cursor object to an Array with .toArray().您可以使用toArray()将Cursor对象转换为Array。

Examples示例

These examples refer to the products collection:这些示例涉及产品系列：

db.products.insertMany([
   { _id: 1, name: 'widget', price: 10.89 },
   { _id: 2, name: 'thing', price: 11.24 },
   { _id: 3, name: 'moppet', price: 8 },
   { _id: 4, name: 'cosa', price: 24.19 }
])

Return a Value From a Collection从集合中返回值

Get the product names.获取产品名称。

db.products.find().map( function(p) { return p.name; } ) ;

Return Results as an Array以Array形式返回结果

Calculate a discounted sale price and return the results as an array.计算折扣销售价格，并将结果作为数组返回。

var salePrices = db.products.find().map( function(p) { return p.price * .9 } ).toArray() ;

Confirm that the output is an Array确认输出是Array

salePrices.constructor.name

Tip

cursor.forEach() for similar functionality.用于类似的功能。