using lodash unique on an array of arrays

Question

I am not sure how to use this to remove duplicate arrays from the main array. so consider the following:

var arr = [
    [0, 1],
    [0, 1],
    [2, 1],
];

The resulting array should look like:

var arr = [
    [0, 1],
    [2, 1],
];

The documentation makes sense for a single array of elements but not a 2d array.

Ideas?

Update, One small issue with some solutions:

The array to be turned unique might have:

var arr = [
  [0, 1]
  [0, 2]
  [0, 3]
  [0, 1]
  [2, 1]
]

the array in side the array should have all value compared, so in the above example, it should spit out:

var arr = [
  [0, 1]
  [0, 2]
  [0, 3]
  [2, 1]
]

The duplicate being [0, 1]

[What](http://stackoverflow.com/help/on-topic) [have](http://stackoverflow.com/help/how-to-ask) [you tried](http://stackoverflow.com/help/mcve)? — rockerest, Nov 03 '15 at 19:47
Will this help: [http://stackoverflow.com/questions/31740155/lodash-remove-duplicates-from-array](http://stackoverflow.com/questions/31740155/lodash-remove-duplicates-from-array) — 2174714, Nov 03 '15 at 19:48

Lukáš Havrlant · Accepted Answer · 2015-11-03T20:39:37.403

4

The easiest way would probably be to use uniq method and then convert the inner arrays to some string representation, JSON.stringify should be good enough solution.

var arr = [[0, 1], [0, 2], [0, 3], [0, 1], [2, 1]]
_.uniq(arr, function(item) { 
    return JSON.stringify(item); 
});
// [[0,1], [0,2], [0,3], [2,1]]

edited Nov 03 '15 at 20:39

answered Nov 03 '15 at 20:21

Lukáš Havrlant

4,134
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18

Do you have example of what this would spit out? – TheWebs Nov 03 '15 at 20:36
4

As of Lodash v4.0.0, you have to use `_.uniqBy` instead – axelstudios Nov 09 '16 at 17:04

score 2 · Answer 2 · answered Nov 03 '15 at 19:48

2

You would use the .uniq function in lodash:

var arr = [
    [0, 1],
    [0, 1],
    [2, 1],
]

var uniqueList = _.uniq(arr, function(item, key, a) { 
    return item.a;
});

The resulting array will look like:

//var arr = [Object: [0, 1], Object: [2, 1]];

answered Nov 03 '15 at 19:48

BlackHatSamurai

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I update my question with a small hitch that I caught when testing your concept. Could you take a look and see if yuor solution can be tweaked to make this work? – TheWebs Nov 03 '15 at 19:54

score 2 · Answer 3 · answered Dec 06 '20 at 18:13

2

Sure, casting to JSON works, but it feels like we might be wasting resources. I'm using the following Lodash-code in Node.js:

const _ = require("lodash");

var arr = [
    [0, 1],
    [0, 1],
    [2, 1],
];

var uni = _.uniqWith(arr, _.isEqual);
console.log(uni);

Works like a charm, check the Repl here. More on uniqWith at the Lodash docs.

answered Dec 06 '20 at 18:13

Kees C. Bakker

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Not sure why this answer had been voted down. It works beautifully. – Rob Jul 29 '22 at 09:27

score -1 · Answer 4 · answered Jul 26 '17 at 13:36

It doesn't use lodash, not optimized I agree :

//remove duplicate array of array of arrays
Array.prototype.uniqueArray = function() {
    var uniqObj = {};
    this.forEach(function (item) {
        uniqObj[JSON.stringify(item)] = 1;
    });

    var uniqArray = [];
    for(var key in uniqObj) {
        if (uniqObj.hasOwnProperty(key)) {
            uniqArray.push(JSON.parse(key))
        }
    }
    return uniqArray;
};

using lodash unique on an array of arrays

Update, One small issue with some solutions:

4 Answers4

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