freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-a-subset-check-on-t...

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---
id: 587d8254367417b2b2512c6f
title: Perform a Subset Check on Two Sets of Data
challengeType: 1
---
## Description
<section id='description'>
In this exercise we are going to perform a subset test on 2 sets of data. We will create a method on our <code>Set</code> data structure called <code>subset</code>. This will compare the first set, against the second and if the first set is fully contained within the Second then it will return true.
For example, if <code>setA = ['a','b']</code> and <code>setB = ['a','b','c','d']</code>, then the subset of setA and setB is: <code>setA.subset(setB)</code> should be <code>true</code>.
</section>
## Instructions
<section id='instructions'>
</section>
## Tests
<section id='tests'>
```yml
tests:
- text: Your <code>Set</code> class should have a <code>subset</code> method.
testString: assert((function(){var test = new Set(); return (typeof test.subset === 'function')})(), 'Your <code>Set</code> class should have a <code>union</code> method.');
- text: The first Set() was contained in the second Set
testString: assert((function(){var setA = new Set(); var setB = new Set(); setA.add('a'); setB.add('b'); setB.add('c'); setB.add('a'); setB.add('d'); var subsetSetAB = setA.subset(setB);return (subsetSetAB === true)})(), 'The first Set() was contained in the second Set');
- text: <code>['a', 'b'].subset(['a', 'b', 'c', 'd'])</code> should return <code>true</code>
testString: assert((function(){var setA = new Set(); var setB = new Set(); setA.add('a'); setA.add('b'); setB.add('a'); setB.add('b'); setB.add('c'); setB.add('d'); var subsetSetAB = setA.subset(setB); return (subsetSetAB === true)})(), "<code>['a', 'b'].subset(['a', 'b', 'c', 'd'])</code> should return <code>true</code>");
- text: <code>['a', 'b', 'c'].subset(['a', 'b'])</code> should return <code>false</code>
testString: assert((function(){var setA = new Set(); var setB = new Set(); setA.add('a'); setA.add('b'); setA.add('c'); setB.add('a'); setB.add('b'); var subsetSetAB = setA.subset(setB); return (subsetSetAB === false)})(), "<code>['a', 'b', 'c'].subset(['a', 'b'])</code> should return <code>false</code>");
- text: <code>[].subset([])</code> should return <code>true</code>
testString: assert((function(){var setA = new Set(); var setB = new Set(); var subsetSetAB = setA.subset(setB); return (subsetSetAB === true)})(), '<code>[].subset([])</code> should return <code>true</code>');
- text: <code>['a', 'b'].subset(['c', 'd'])</code> should return <code>false</code>
testString: assert((function(){var setA = new Set(); var setB = new Set(); setA.add('a'); setA.add('b'); setB.add('c'); setB.add('d'); var subsetSetAB = setA.subset(setB); return (subsetSetAB === false)})(), "<code>['a', 'b'].subset(['c', 'd'])</code> should return <code>false</code>");
```
</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 collection
this.size = function() {
return collection.length;
};
// this method will return the union of two sets
this.union = function(otherSet) {
var unionSet = new Set();
var firstSet = this.values();
var secondSet = otherSet.values();
firstSet.forEach(function(e){
unionSet.add(e);
});
secondSet.forEach(function(e){
unionSet.add(e);
});
return unionSet;
};
// this method will return the intersection of two sets as a new set
this.intersection = function(otherSet) {
var intersectionSet = new Set();
var firstSet = this.values();
firstSet.forEach(function(e){
if(otherSet.has(e)){
intersectionSet.add(e);
}
});
return intersectionSet;
};
// this method will return the difference of two sets as a new set
this.difference = function(otherSet) {
var differenceSet = new Set();
var firstSet = this.values();
firstSet.forEach(function(e){
if(!otherSet.has(e)){
differenceSet.add(e);
}
});
return differenceSet;
};
// 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;};this.intersection = function(set) {var i = new Set();var c = this.values();c.forEach(function(element){if(s.has(element)) i.add(element);});};this.difference = function(set) {var d = new Set();var c = this.values();c.forEach(function(e){if(!set.has(e)) d.add(e);});};this.subset = function(set) {var isSubset = true;var c = this.values();c.forEach(function(e){if(!set.has(e)) isSubset = false;});return isSubset;};}
```
</section>