freeCodeCamp/curriculum/challenges/en/08-coding-interview-prep/data-structures/perform-a-union-on-two-sets.en.md

---
id: 587d8253367417b2b2512c6c
title: Perform a Union on Two Sets
challengeType: 1
---

## Description
<section id='description'>
In this exercise we are going to perform a union on two sets of data. We will create a method on our <code>Set</code> data structure called <code>union</code>. This method should take another <code>Set</code> as an argument and return the <code>union</code> of the two sets, excluding any duplicate values.
For example, if <code>setA = ['a','b','c']</code> and <code>setB = ['a','b','d','e']</code>, then the union of setA and setB is: <code>setA.union(setB) = ['a', 'b', 'c', 'd', 'e']</code>.
</section>

## Instructions
<section id='instructions'>

</section>

## Tests
<section id='tests'>

```yml
- text: Your <code>Set</code> class should have a <code>union</code> method.
  testString: 'assert((function(){var test = new Set(); return (typeof test.union === ''function'')})(), ''Your <code>Set</code> class should have a <code>union</code> method.'');'
- text: The proper collection was returned
  testString: 'assert((function(){var setA = new Set();  var setB = new Set();  setA.add(''a'');  setA.add(''b'');  setA.add(''c'');  setB.add(''c'');  setB.add(''d'');  var unionSetAB = setA.union(setB); var final = unionSetAB.values(); return (final.indexOf(''a'') !== -1 && final.indexOf(''b'') !== -1 && final.indexOf(''c'') !== -1 && final.indexOf(''d'') !== -1 && final.length === 4)})(), ''The proper collection was returned'');'

```

</section>

## Challenge Seed
<section id='challengeSeed'>

<div id='js-seed'>

```js
function Set() {
    // the var collection will hold the set
    var collection = [];
    // this method will check for the presence of an element and return true or false
    this.has = function(element) {
        return (collection.indexOf(element) !== -1);
    };
    // this method will return all the values in the set
    this.values = function() {
        return collection;
    };
    // this method will add an element to the set
    this.add = function(element) {
        if(!this.has(element)){
            collection.push(element);
            return true;
        }
        return false;
    };
   // this method will remove an element from a set
    this.remove = function(element) {
        if(this.has(element)){
           var index = collection.indexOf(element);
            collection.splice(index,1);
            return true;
        }
        return false;
    };
    // this method will return the size of the set
    this.size = function() {
        return collection.length;
    };
    // change code below this line

    // change code above this line
}
```

</div>



</section>

## Solution
<section id='solution'>


```js
function Set() {var collection = []; this.has = function(e){return(collection.indexOf(e) !== -1);};this.values = function() {return collection;};this.add = function(element) {if (!this.has(element)) {collection.push(element);return true;} else {return false;}};this.remove = function(element) {if(this.has(element)) {var i = collection.indexOf(element);collection.splice(i, 1);return true;}return false;};this.size = function() {return collection.length;};this.union = function(set) {var u = new Set();var c = this.values();var s = set.values();c.forEach(function(element){u.add(element);});s.forEach(function(element){u.add(element);});return u;};}
```

</section>