freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/data-structures/create-a-set-class.english.md

id	title	challengeType
8d1323c8c441eddfaeb5bdef	Create a Set Class	1

Description

In the next few exercises we are going to create a function to emulate a data structure called a "Set". A Set is like an array, but it cannot contain duplicate values. The typical use for a Set is to simply check for the presence of an item. This can be implemented with an object, for instance:

var set = new Object();
set.foo = true;
// See if foo exists in our set:
console.log(set.foo) // true

In the next few exercises, we will build a full featured Set from scratch. For this exercise, create a function that will add a value to our set collection as long as the value does not already exist in the set. For example:

this.add = function(element) {
//some code to add value to the set
}

The function should return true if the value is successfully added and false otherwise.

Instructions

Tests

tests:
  - text: Your <code>Set</code> class should have an <code>add</code> method.
    testString: assert((function(){var test = new Set(); return (typeof test.add === 'function')}()), 'Your <code>Set</code> class should have an <code>add</code> method.');
  - text: Your <code>add</code> method should not add duplicate values.
    testString: assert((function(){var test = new Set(); test.add('a'); test.add('b'); test.add('a'); var vals = test.values(); return (vals[0] === 'a' && vals[1] === 'b' && vals.length === 2)}()), 'Your <code>add</code> method should not add duplicate values.');
  - text: Your <code>add</code> method should return <code>true</code> when a value has been successfully added.
    testString: assert((function(){var test = new Set(); var result = test.add('a'); return (result != undefined) && (result === true);}()), 'Your <code>add</code> method should return <code>true</code> when a value has been successfully added.');
  - text: Your <code>add</code> method should return <code>false</code> when a duplicate value is added.
    testString: assert((function(){var test = new Set(); test.add('a'); var result = test.add('a'); return (result != undefined) && (result === false);}()), 'Your <code>add</code> method should return <code>false</code> when a duplicate value is added.');

Challenge Seed

function Set() {
    // the var collection will hold our 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;
    };
    // change code below this line
    // change code above this line
}

Solution

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;}};}