How to remove duplicates from an array of objects?

Question

What the best way to remove duplicates from an array of objects?

var array = [
  {a: 0, b: 0, c: 0},
  {a: 0, b: 0, c: 0},

  {a: 1, b: 1, c: 1},
  {a: 1, b: 1, c: 1},

   //..... etc
];

And, i want to get like:

[
  {a: 0, b: 0, c: 0},
  {a: 1, b: 1, c: 1}
];

PS: the keys (a, b, c) have only primitive data type (String, Number)

Please, without underscore.js and other libs.

What is your equality function? I.e. what does it mean for two objects to be duplicative of one another? Are you assuming no-one will mutate elements of this array? — Mike Samuel
– Mike Samuel, Commented Jan 31, 2013 at 19:42
@Dancrumb, I dont want to use the underscore.js in my project, because there're no any reasons for it — Robbin
– Robbin, Commented Jan 31, 2013 at 22:50

Tomas Ramirez Sarduy · Accepted Answer · 2013-01-31 21:04:39Z

2

I'm sure there is better ways to do this, but you can use this prototype function.

Array.prototype.removeDuplicates = function () {
    var r = new Array();
    o:for(var i = 0, n = this.length; i < n; i++)
    {
        for(var x = 0, y = r.length; x < y; x++)
            if(r[x].a==this[i].a && r[x].b==this[i].b && r[x].c==this[i].c)
                continue o;
        r.push(this[i]);
    }
    return r;
}

How to use it

var arr = [
  {a: 0, b: 0, c: 0},
  {a: 0, b: 0, c: 0},
  {a: 1, b: 1, c: 1},
  {a: 1, b: 1, c: 1},

   //..... etc
];
var uniques = arr.removeDuplicates();
console.log(uniques);

Note:

You should avoid this for big arrays, out there are better solutions

answered Jan 31, 2013 at 21:04

Tomas Ramirez Sarduy

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5 Comments

Robbin Over a year ago

Could you rewrite your example without o: ?

Tomas Ramirez Sarduy Over a year ago

@Robbin: I think a better idea is that you rewrite the code. Hint: use a bit (value 0 or 1) inside loop

Lion789 Over a year ago

How big of arrays should be avoided, and I have been looking, anyone have a link or can state a better solution, I have the same issue but have arrays with a couple thousand objects to go through...

Tomas Ramirez Sarduy Over a year ago

@Lion789: In that case you need to study algorithms for that and maybe some heuristics

Lion789 Over a year ago

Ok, by the way, using the above prototype, how would you go about removing duplicates and merging two or more arrays?

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