cursor.map()
cursor.map(function)Important
mongosh Method
This page documents a
mongoshmethod. This is not the documentation for a language-specific driver, such as Node.js.For MongoDB API drivers, refer to the language-specific MongoDB driver documentation.
Applies a
functionto each document visited by the cursor and collects the return values from successive applications of thefunctioninto aCursorobject.The
cursor.map()method has the following parameter:ParameterTypeDescriptionfunctionfunctionA 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