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cursor.map()

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  • Behavior
  • Examples
cursor.map(function)

Important

mongosh Method

This is a mongosh method. This is not the documentation for Node.js or other programming language specific driver methods.

In most cases, mongosh methods work the same way as the legacy mongo shell methods. However, some legacy methods are unavailable in mongosh.

For the legacy mongo shell documentation, refer to the documentation for the corresponding MongoDB Server release:

For MongoDB API drivers, refer to the language specific MongoDB driver documentation.

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.

The cursor.map() method has the following parameter:

Parameter
Type
Description
function
function
A function to apply to each document visited by the cursor.

Behavior

cursor.map() returns a Cursor object. Note that .map() only converts the type, it does not create a new cursor. You can convert the Cursor object to an Array with .toArray().

Examples

These examples refer to the products collection:

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

Get the product names.

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

Return Results as an Array

Calculate a discounted sale price and return the results as an array.

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

Confirm that the output is an Array

salePrices.constructor.name

Tip

See also:

cursor.forEach() for similar functionality.

←  cursor.limit()cursor.max() →

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