Arrays - Storing Multiple Values

What Is an Array?

An array is a special kind of variable that lets you store a list of values together. Instead of a single wire that connects a name to one value, imagine an array as a long wire with many slots—each holding a single value. These slots are called indices, and they are numbered starting at 0.

For example, consider the following array:

let fruits = ["apple", "banana", "cherry"];

In this code we declare a variable fruits using let and assign it an array of three string values. Each value is stored at a specific index:

• "apple" is at index 0
• "banana" is at index 1
• "cherry" is at index 2

Creating an Array

To create an array, you use square brackets with a comma-separated list of values:

let numbers = [1, 2, 3, 4];

You can also create an empty array and add values later:

let emptyArray = [];
emptyArray[0] = "first";
emptyArray[1] = "second";

Accessing Array Elements

You can access an element by using its index. For example, to get the first element of the fruits array, you write:

console.log(fruits[0]); // prints "apple"

The number inside the square brackets tells JavaScript which item you want to read.

fruits[1] = "blueberry";
console.log(fruits); // prints ["apple", "blueberry", "cherry"]

Updating Array Elements

You can change the value at any index. For example, if you want to change "banana" to "blueberry" in the fruits array:

fruits[1] = "blueberry";
console.log(fruits); // prints ["apple", "blueberry", "cherry"]

This “reconnects” the wire at index 1 to a new value.

Adding Elements with push()

The push() method lets you add a new value to the end of an array. Imagine that your array is a long wire with several connection points, and push() attaches a new connection at the end.

For example:

let colors = ["red", "green"];
colors.push("blue");
console.log(colors); // prints ["red", "green", "blue"]

Removing Elements with pop()

The pop() method removes the last element from an array. It “disconnects” the final connection point from the wire and returns the removed value.

For example:

let numbers = [1, 2, 3, 4];
let removed = numbers.pop();
console.log(numbers); // prints [1, 2, 3]
console.log(removed); // prints 4

Exercises