Theincludes() method ofArray instances determines whether an arrayincludes a certain value among its entries, returningtrue orfalse as appropriate.

Try it

const array = [1, 2, 3];console.log(array.includes(2));// Expected output: trueconst pets = ["cat", "dog", "bat"];console.log(pets.includes("cat"));// Expected output: trueconsole.log(pets.includes("at"));// Expected output: false

Syntax

includes(searchElement)includes(searchElement, fromIndex)

Parameters

searchElement

The value to search for.

fromIndexOptional

Zero-based index at which to start searching,converted to an integer.

• Negative index counts back from the end of the array — if-array.length <= fromIndex < 0,fromIndex + array.length is used. However, the array is still searched from front to back in this case.
• IffromIndex < -array.length orfromIndex is omitted,0 is used, causing the entire array to be searched.
• IffromIndex >= array.length, the array is not searched andfalse is returned.

Return value

A boolean value which istrue if the valuesearchElement is found within the array (or the part of the array indicated by the indexfromIndex, if specified).

Description

Theincludes() method comparessearchElement to elements of the array using theSameValueZero algorithm. Values of zero are all considered to be equal, regardless of sign. (That is,-0 is equal to0), butfalse isnot considered to be the same as0.NaN can be correctly searched for.

When used onsparse arrays, theincludes() method iterates empty slots as if they have the valueundefined.

Theincludes() method isgeneric. It only expects thethis value to have alength property and integer-keyed properties.

Examples

Using includes()

[1, 2, 3].includes(2); // true[1, 2, 3].includes(4); // false[1, 2, 3].includes(3, 3); // false[1, 2, 3].includes(3, -1); // true[1, 2, NaN].includes(NaN); // true["1", "2", "3"].includes(3); // false

fromIndex is greater than or equal to the array length

IffromIndex is greater than or equal to the length of thearray,false is returned. The array will not be searched.

const arr = ["a", "b", "c"];arr.includes("c", 3); // falsearr.includes("c", 100); // false

Computed index is less than 0

IffromIndex is negative, the computed index is calculated tobe used as a position in the array at which to begin searching forsearchElement. If the computed index is less than or equal to0, the entire array will be searched.

// array length is 3// fromIndex is -100// computed index is 3 + (-100) = -97const arr = ["a", "b", "c"];arr.includes("a", -100); // truearr.includes("b", -100); // truearr.includes("c", -100); // truearr.includes("a", -2); // false

Using includes() on sparse arrays

You can search forundefined in a sparse array and gettrue.

console.log([1, , 3].includes(undefined)); // true

Calling includes() on non-array objects

Theincludes() method reads thelength property ofthis and then accesses each property whose key is a nonnegative integer less thanlength.

const arrayLike = {  length: 3,  0: 2,  1: 3,  2: 4,  3: 1, // ignored by includes() since length is 3};console.log(Array.prototype.includes.call(arrayLike, 2));// trueconsole.log(Array.prototype.includes.call(arrayLike, 1));// false

Specifications

Browser compatibility

See also

• Polyfill ofArray.prototype.includes incore-js
• es-shims polyfill ofArray.prototype.includes
• Indexed collections guide
• Array
• Array.prototype.indexOf()
• Array.prototype.find()
• Array.prototype.findIndex()
• TypedArray.prototype.includes()
• String.prototype.includes()