freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-data-structures/use-an-array-to-store-a-collection-of-data.english.md

id, title, challengeType, forumTopicId

id	title	challengeType	forumTopicId
587d7b7e367417b2b2512b20	Use an Array to Store a Collection of Data	1	301167

Description

The below is an example of the simplest implementation of an array data structure. This is known as a one-dimensional array, meaning it only has one level, or that it does not have any other arrays nested within it. Notice it contains booleans, strings, and numbers, among other valid JavaScript data types:

let simpleArray = ['one', 2, 'three', true, false, undefined, null];
console.log(simpleArray.length);
// logs 7

All arrays have a length property, which as shown above, can be very easily accessed with the syntax Array.length. A more complex implementation of an array can be seen below. This is known as a multi-dimensional array, or an array that contains other arrays. Notice that this array also contains JavaScript objects, which we will examine very closely in our next section, but for now, all you need to know is that arrays are also capable of storing complex objects.

let complexArray = [
  [
    {
      one: 1,
      two: 2
    },
    {
      three: 3,
      four: 4
    }
  ],
  [
    {
      a: "a",
      b: "b"
    },
    {
      c: "c",
      d: "d"
    }
  ]
];

Instructions

We have defined a variable called yourArray. Complete the statement by assigning an array of at least 5 elements in length to the yourArray variable. Your array should contain at least one string, one number, and one boolean.

Tests

tests:
  - text: <code>yourArray</code> should be an array.
    testString: assert.strictEqual(Array.isArray(yourArray), true);
  - text: <code>yourArray</code> should be at least 5 elements long.
    testString: assert.isAtLeast(yourArray.length, 5);
  - text: <code>yourArray</code> should contain at least one <code>boolean</code>.
    testString: assert(yourArray.filter( el => typeof el === 'boolean').length >= 1);
  - text: <code>yourArray</code> should contain at least one <code>number</code>.
    testString: assert(yourArray.filter( el => typeof el === 'number').length >= 1);
  - text: <code>yourArray</code> should contain at least one <code>string</code>.
    testString: assert(yourArray.filter( el => typeof el === 'string').length >= 1);

Challenge Seed

let yourArray; // change this line

Solution

let yourArray = ['a string', 100, true, ['one', 2], 'another string'];