JavaScript (ES2026) reference · Array Methods

JavaScript Array includes() Method

Return true if the array contains a value, using SameValueZero equality (so it finds NaN, unlike indexOf).

JavaScript (ES2026) Since ES2016

Syntax

array.includes(searchElement, fromIndex)

Parameter	Description
`searchElement`	The value to look for.
`fromIndex` optional	Index to start searching from. Default: `0`

true or false.

Is it in the array?Try it yourself

const pets = ["cat", "dog"];
console.log(pets.includes("dog"), pets.includes("bird"));

Output

true false

includes() finds NaNTry it yourself

console.log([NaN].includes(NaN), [NaN].indexOf(NaN));

Output

true -1

Objects are compared by referenceTry it yourself

const users = [{ id: 1 }];
console.log(users.includes({ id: 1 })); // different object
console.log(users.some((u) => u.id === 1));

Output

false
true

Version	Change
JavaScript ES2016	Added

array.indexOf() · Return the first index at which a value is found (using ===), or -1 if it isn't in the array.
array.some() · Return true if at least one element passes a test function. Stops at the first match; an empty array returns false.
array.find() · Return the first element that passes a test function, or undefined if none does.
JavaScript Arrays · tutorial
JavaScript Array Methods · tutorial