Question

132

How to find duplicate values in a JavaScript array of objects, and output only unique values?

rated 0 times [ 134] [ 2] / answers: 1 / hits: 92390 / 8 Years ago, thu, october 6, 2016, 12:00:00

I'm learning JS. Supposing I have the below array of objects:

var family = [

  {

    name: Mike,

    age: 10

  },

  {

    name: Matt

    age: 13

  },

  {

    name: Nancy,

    age: 15

  },

  {

    name: Adam,

    age: 22

  },

  {

    name: Jenny,

    age: 85

  },

  {

    name: Nancy,

    age: 2

  },

  {

    name: Carl,

    age: 40

  }

];

Notice that Nancy is showing up twice (changing only the age). Supposing I want to output only unique names. How do I output the above array of objects, without duplicates? ES6 answers more than welcome.

Related (couldn't find a good way for usage on objects):

Remove Duplicates from JavaScript Array

Easiest way to find duplicate values in a JavaScript array

EDIT Here's what I tried. It works well with strings but I can't figure how to make it work with objects:

family.reduce((a, b) => {

  if (a.indexOf(b) < 0 ) {

    a.push(b);

  }

  return a;

},[]);

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paolam

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answered 8 Years ago jaelyn · Accepted Answer

You could use a Set in combination with Array#map and a spread operator ... in a single line.

Map returns an array with all names, which are going into the set initializer and then all values of the set are returned in an array.

var family = [{ name: Mike, age: 10 }, { name: Matt, age: 13 }, { name: Nancy, age: 15 }, { name: Adam, age: 22 }, { name: Jenny, age: 85 }, { name: Nancy, age: 2 }, { name: Carl, age: 40 }],

    unique = [...new Set(family.map(a => a.name))];



console.log(unique);

For filtering and return only unique names, you can use Array#filter with Set.

var family = [{ name: Mike, age: 10 }, { name: Matt, age: 13 }, { name: Nancy, age: 15 }, { name: Adam, age: 22 }, { name: Jenny, age: 85 }, { name: Nancy, age: 2 }, { name: Carl, age: 40 }],

    unique = family.filter((set => f => !set.has(f.name) && set.add(f.name))(new Set));



console.log(unique);