How do you create and access arrays in JavaScript?

An array is an ordered list of values addressed by a numeric index that starts at 0.

An array is JavaScript's way of holding a sequence of values in one variable. Conceptually it's a set of key-value pairs where the keys are whole numbers starting at 0 — so the first element lives at index 0, the second at 1, and so on. You create one with square brackets:

let animals = ['lion', 'rat'];   // index 0 is 'lion', index 1 is 'rat'

console.log(animals[0]);   // 'lion'
console.log(animals[1]);   // 'rat'

animals[1] = 'fish';       // replace 'rat' with 'fish'
animals[2] = 'crocodile';  // add a new element at index 2

Key points and the classic gotcha:

• Indices start at 0, not 1 — so a 3-element array has indices 0, 1, 2. Off-by-one mistakes here are extremely common.
• Arrays can hold mixed types: [1, 'hello', true] is perfectly valid.
• Arrays are dynamic — they grow and shrink as you add or remove elements; you don't fix a size up front.

Go deeper:

• MDN: Indexed collections — creating and indexing arrays, the length property, and the full set of built-in array methods.