Linear Search and When to Use It

Written by Swapnil RajaPublished 28 Aug 2026

Linear search is the one everybody dismisses. On the sizes most code actually deals with, it is frequently the fastest option and always the clearest.

The built-ins are all linear

Five ways to scan

javascript

const users = [{ id: 1, name: "Ada" }, { id: 2, name: "Grace" }]

users.find((u) => u.id === 2)       // the element, or undefined
users.findIndex((u) => u.id === 2)  // the index, or -1
users.some((u) => u.id === 2)       // true or false
users.filter((u) => u.id > 1)       // every match
;[1, 2, 3].includes(2)              // primitives only

PreviousBinary Search Explained NextHeaps and Priority Queues

When indexing pays for itself

javascript

const users = [{ id: 1 }, { id: 2 }, { id: 3 }]
const target = 2

// One lookup: scanning wins.
const found = users.find((u) => u.id === target)   // O(n), zero setup

// Many lookups: index once, then O(1) each.
const byId = new Map(users.map((u) => [u.id, u]))  // O(n) once
byId.get(target)                                    // O(1) forever after

Stop as soon as you know

javascript

const users = [{ isAdmin: false }, { isAdmin: true }, { isAdmin: false }]

// Walks all million even after finding a match.
const anyAdmin = users.filter((u) => u.isAdmin).length > 0

// Stops at the first one.
const anyAdmin2 = users.some((u) => u.isAdmin)

Linear Search and When to Use It

The built-ins are all linear

When linear is genuinely right

Doing the arithmetic

Early exit is worth more than it looks

The honest summary