Array Methods (map, filter, reduce) — Free JavaScript Tutorial

TL;DR: Learn Array Methods (map, filter, reduce) in JavaScript with a free, beginner-friendly tutorial, examples and practice for Indian students on Syllab.i…

Array Methods (map, filter, reduce) in JavaScript

Modern JavaScript array methods process arrays without for loops. They are cleaner, more readable, and chainable.

map() transforms each element and returns a NEW array. filter() keeps only elements that pass a test. reduce() accumulates all elements into a single value.

find() returns the first matching element. some() checks if ANY element passes. every() checks if ALL pass. forEach() runs a function on each (no return).

These methods can be chained: students.filter(s => s.marks >= 60).map(s => s.name) — get names of passing students.

const nums = [1, 2, 3, 4, 5];

nums.map(n => n * 2)          // [2, 4, 6, 8, 10]
nums.filter(n => n % 2 === 0) // [2, 4]
nums.reduce((sum, n) => sum + n, 0) // 15
nums.find(n => n > 3)         // 4
nums.some(n => n > 4)         // true
nums.every(n => n > 0)        // true

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