Arrays and Array Methods

Arrays are ordered collections of values. They are one of the most frequently used data structures in JavaScript, and the language provides a rich set of built-in methods for working with them.

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Creating Arrays

// Array literal (preferred)
const fruits = ["apple", "banana", "cherry"];

// Array constructor
const numbers = new Array(1, 2, 3);

// Empty array
const empty = [];

// Array.of() — creates an array from arguments
const single = Array.of(5); // [5] (not an empty array of length 5)

// Array.from() — creates an array from an iterable or array-like object
const letters = Array.from("hello"); // ["h", "e", "l", "l", "o"]

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Accessing and Modifying Elements

const colours = ["red", "green", "blue"];

// Access by index (zero-based)
console.log(colours[0]);   // "red"
console.log(colours[2]);   // "blue"

// Modify an element
colours[1] = "yellow";
console.log(colours);      // ["red", "yellow", "blue"]

// Array length
console.log(colours.length); // 3

// Access the last element
console.log(colours[colours.length - 1]); // "blue"
console.log(colours.at(-1));              // "blue" (ES2022)

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Adding and Removing Elements