Lists with Arrays

Storing many values in one place

9 min read · runnable Javascript

So far each variable held a single value. But what if you have a shopping list, or a group of scores? For that we use an array, which is an ordered list of values.

You create an array with square brackets [ ], separating each item with a comma.

let fruits = ["apple", "banana", "cherry"];
console.log(fruits);

Getting an item out

Each item has a position number called its index. Here is the surprising part: counting starts at 0, not 1.

let fruits = ["apple", "banana", "cherry"];
console.log(fruits[0]); // apple
console.log(fruits[1]); // banana
console.log(fruits[2]); // cherry

Tip: The first item is always at index 0. This trips up almost everyone at first, so it is worth saying again: the count starts at zero.

How many items?

Every array knows its own length. Ask for it with .length:

console.log(fruits.length); // 3

Adding an item

You can add a new item to the end with .push:

fruits.push("date");
console.log(fruits); // apple, banana, cherry, date

Try it yourself

Run the code, then add another fruit of your choice.

Try it yourself

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

console.log(fruits[0]);          // first item
console.log(fruits.length);      // how many items

fruits.push("date");             // add to the end
console.log(fruits);

Output

Press “Run code” to see the result.

Quick check

Q1 In the array ["a", "b", "c"], what index does "a" have?

Q2 What does fruits.length tell you?

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