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]

Will this help: http://stackoverflow.com/questions/31740155/lodash-remove-duplicates-from-array — 2174714
– 2174714, Commented Nov 3, 2015 at 19:48

Lukáš Havrlant · Accepted Answer · 2015-11-03 20:39:37Z

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 3, 2015 at 20:39

answered Nov 3, 2015 at 20:21

Lukáš Havrlant

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2 Comments

TheWebs Over a year ago

Do you have example of what this would spit out?

axelstudios Over a year ago

As of Lodash v4.0.0, you have to use _.uniqBy instead

BlackHatSamurai · Accepted Answer · 2015-11-03 19:48:07Z

3

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 3, 2015 at 19:48

BlackHatSamurai

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1 Comment

TheWebs Over a year ago

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?

Kees C. Bakker · Accepted Answer · 2020-12-06 18:13:02Z

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 6, 2020 at 18:13

Kees C. Bakker

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1 Comment

Rob Over a year ago

Not sure why this answer had been voted down. It works beautifully.

Remy Mellet · Accepted Answer · 2017-07-26 13:36:34Z

-1

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;
};

answered Jul 26, 2017 at 13:36

Remy Mellet

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