Underscore.js - get unique property values

Question

I only recently discovered the power of underscore.js, still new to the methods I kindly ask for a suggestion:

How do I get from this:

[
    [{
        "name": "Type 2",
        "id": 14
    }],
    [{
        "name": "Type 1",
        "id": 13
    }, {
        "name": "Type 3",
        "id": 15
    }],
    [{
        "name": "Type 2",
        "id": 14
    }],
    [{
        "name": "Type 1",
        "id": 13
    }]
]

to this:

["Type 1","Type 2","Type 3"]

i.e. no duplicated and "name" property only.

Any suggestions much appreciated.

@BlackSheep - I was able to do this in couple of steps. But I was missing the `flatten` method which makes the chaining possible. — Iladarsda, Feb 04 '14 at 16:28

score 28 · Accepted Answer · answered Feb 04 '14 at 16:14

28

_(data).chain().flatten().pluck('name').unique().value()

(Convert the nested lists to a flat one, pick name from each of the objects in the list, and make it unique.)

answered Feb 04 '14 at 16:14

Jakub Roztocil

15,930
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1

Is there any particular merit to chaining methods in underscore/lo-dash compared to nesting (as in McGarnagle's answer). Or is it purely for aesthetics/code clarity? – nverba Jul 08 '14 at 10:09
In lodash it is more efficient if you create a wrapper with `_()` if you chain multiple methods together, less efficient if you only do one (maybe two) operations. Do your own benchmarks for each situation. – kmiyashiro Mar 11 '15 at 23:38

McGarnagle · Answer 2 · 2014-02-04T16:20:55.090

10

Use flatten first, to convert the nested array to a flat array.
Then pluck to get the "name" values as an array
Finally uniq

_.uniq(_.pluck(_.flatten(items), "name"))

Fiddle

edited Feb 04 '14 at 16:20

answered Feb 04 '14 at 16:14

McGarnagle

101,349
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score 3 · Answer 3 · edited Dec 13 '15 at 17:15

3

_.uniq(_.pluck(x,'name'));

the above code is sufficient for extracting different "name" attribute

edited Dec 13 '15 at 17:15

JDurstberger

4,127
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answered Dec 13 '15 at 15:54

Praveen Gubbala

71
3

score 2 · Answer 4 · answered Feb 04 '14 at 16:32

2

var arr = _.uniq(_.map(_.flatten(array), function(e) {
    return e.name;
}));

answered Feb 04 '14 at 16:32

Alex_Crack

710
1
4
14

Lộc Đoàn Đình · Answer 5 · 2018-07-15T15:19:52.653

1

Simple way:

1. use _.map to get all the names

var names = _.map(items, function(item) { return item.name});

2. Get the _.uniq from that names

var uniqueNames = _.uniq(names);

edited Jul 15 '18 at 15:19

answered Jul 15 '18 at 15:12

Lộc Đoàn Đình

29
2

Underscore.js - get unique property values

5 Answers5

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