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MongoDB Tutorial

MongoDB: cursor.map() method

cursor.map

The cursor.map() method is used to apply a function to each document by a cursor and collects the return values from successive application into in an array.

Syntax:

cursor.map()

Parameters:

Name Description Required /
Optional
Type
function A function to apply to each document visited by the cursor. Required function

Sample document in the restaurants collection:


{
  "address": {
     "building": "1007",
     "coord": [ -73.856077, 40.848447 ],
     "street": "Morris Park Ave",
     "zipcode": "10462"
  },
  "borough": "Bronx",
  "cuisine": "Bakery",
  "grades": [
     { "date": { "$date": 1393804800000 }, "grade": "A", "score": 2 },
     { "date": { "$date": 1378857600000 }, "grade": "A", "score": 6 },
     { "date": { "$date": 1358985600000 }, "grade": "A", "score": 10 },
     { "date": { "$date": 1322006400000 }, "grade": "A", "score": 9 },
     { "date": { "$date": 1299715200000 }, "grade": "B", "score": 14 }
  ],
  "name": "Morris Park Bake Shop",
  "restaurant_id": "30075445"
}
......

Example: MongoDB: cursor.map() method

The following example will retrieve all the documents from the collection restaurants which matches the query criteria cuisine is Indian and collect the return value into an array.

db.restaurants.find({cuisine : "Indian"}).map( function(u) { return u.cuisine; } );

Output:

> db.restaurants.find({cuisine : "Indian"}).map( function(u) { return u.cuisine; } );
[
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
        "Indian",
		...
]		

Retrieve the restaurants data from here

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