JavaScript Array Methods#

Arrays are one of the most commonly used data structures in JavaScript. Here are the most important methods.

Transformation Methods

map()

Transforms each element of the array by applying a function:

const numbers = [1, 2, 3, 4, 5];
const doubled = numbers.map(n => n * 2);
// [2, 4, 6, 8, 10]

filter()

Filters elements that meet a condition:

const numbers = [1, 2, 3, 4, 5];
const evens = numbers.filter(n => n % 2 === 0);
// [2, 4]

reduce()

Reduces the array to a single value:

const numbers = [1, 2, 3, 4, 5];
const sum = numbers.reduce((acc, n) => acc + n, 0);
// 15

Search Methods

find()

Finds the first element that meets the condition:

const users = [
  { id: 1, name: 'Ana' },
  { id: 2, name: 'John' }
];
const user = users.find(u => u.id === 2);
// { id: 2, name: 'John' }

includes()

Checks if an element exists in the array:

const fruits = ['apple', 'banana', 'orange'];
fruits.includes('banana'); // true

Best Practices

1. Use map() when you need to transform all elements
2. Use filter() when you need to filter elements
3. Use find() when looking for a single element
4. Avoid modifying the original array when possible