What is an array?

An array is a data structure that groups together data.. The data can be strings, numbers, booleans, or any mix of these data types.

Syntax

Inside an array is a comma separated list of data. An array starts and ends with a square brackets [].

['bananas', 'oranges']; // this is an array - without a variable name to reference
let anArrayOfNumbers = [9, 1, 2, 4, 4, 5];
let anArrayOfFruits = ['pineapples', 'bananas', 'oranges'];
let aMixedArray = ['hello', 4, true, 'peace', 1002];

Access

To have access to an array item you use the index of the item within square brackets. Note the first item's index is 0.

let anArrayOfFruits = ['pineapples', 'bananas', 'oranges'];
console.log(anArrayOfFruits[1]); // prints 'bananas'

Properties

length

The length property tells you the length of the array.

let anArrayOfNumbers = [9, 1, 2, 4, 4, 5];
console.log(anArrayOfNumbers.length);
// prints 6

Methods

pop()

The pop() method removes the last item of the array.

let anArrayOfNumbers = [9, 1, 2, 4, 4, 5];
console.log(anArrayOfNumbers); // prints [9, 1, 2, 4, 4, 5]
anArrayOfNumbers.pop();
console.log(anArrayOfNumbers); // prints [9, 1, 2, 4, 4]

push()

The push() method adds an item onto the end of the array.

let anArrayOfNumbers = [9, 1, 2, 4, 4, 5];
console.log(anArrayOfNumbers); // prints [9, 1, 2, 4, 4, 5]
anArrayOfNumbers.push(12);
console.log(anArrayOfNumbers); // prints [9, 1, 2, 4, 4, 5, 12]

reverse()

An array reverses the data in an array.

let anArrayOfNumbers = [9, 1, 2, 4, 4, 5];
console.log(anArrayOfNumbers); // prints [9, 1, 2, 4, 4, 5]
anArrayOfNumbers.reverse();
console.log(anArrayOfNumbers); // prints [5, 4, 4, 2, 1, 9]