Question

The data structure in mongodb is
 {'_id': 1, 'name': 'a'}
 {'_id': 2, 'name': 'b'}
 {'_id': 3, 'name': 'c'}
 
 Can now pass
 db.collection.find({}, {'name': 1})
 The resulting list is:
 [
 {'name': 'a'},
 {'name': 'b'},
 {'name': 'c'}
 ]
 
 Is there any way to get the following values (don't want to load the data into the memory recycle list for processing, does mongodb itself provide any method)
 ['a', 'b', 'c']

Answer 1

Mongodb supports js syntax, so use it directly.mapJust do it

// es6
 db.collection.find({}, {'name': 1}).map( x => x.name ) // [ "a", "b", "c" ]
 
 db.collection.find({}, {'name': 1}).map(function(x) {return x.name} )

Please see map introduction.https://danmartensen.svbtle.com/javascripts-map-reduce-and-filter#map_1