JavaScript Array includes() Method

JavaScript Array includes() method determines whether an array contains a specific value or not. It returns a boolean value (true or false) based on whether the specified value exists in the array.

Pre-requisites to Learn

JavaScript Array

Syntax

arr.includes(valueToFind, fromIndex);

Parameters

Parameter	Description
valueToFind (Required)	The value to search for in the array.
fromIndex (Optional)	The index to start the search from. Defaults to `0`. If negative, it counts from the end of the array.

Return Value

The includes() method returns true if the specified value is found in the array, otherwise returns false.

Notes:

The search is case-sensitive for strings.
Unlike indexOf(), the includes() method can correctly detect NaN as a valid value in the array.
It does not modify the original array.

Examples of JavaScript Array includes() Method

Example 1: Checking whether specific fruits are present in the array.

let fruits = ['apple', 'banana', 'cherry'];

console.log(fruits.includes('banana')); // Output: true
console.log(fruits.includes('grape'));  // Output: false

Example 2: The includes() method is case-sensitive i.e. the 'apple' and 'Apple' are treated as different values.

let fruits = ['Apple', 'Banana', 'Cherry'];

console.log(fruits.includes('apple')); // Output: false
console.log(fruits.includes('Apple')); // Output: true

Example 3: The fromIndex parameter specifies where the search should start. Negative values count backward from the end of the array.

let numbers = [10, 20, 30, 40, 50];

console.log(numbers.includes(30, 2));  // Output: true
console.log(numbers.includes(30, 3));  // Output: false
console.log(numbers.includes(30, -3)); // Output: true

Example 4: Handling NaN Values – Unlike indexOf(), which cannot detect NaN, the includes() method correctly identifies its presence.

let values = [1, 2, NaN, 4];

console.log(values.includes(NaN)); // Output: true

Example 5: In sparse arrays, empty slots are treated as undefined by the includes() method.

let sparseArray = [1, , 3];

console.log(sparseArray.includes(undefined)); // Output: true

Supported Browsers

Browser	Support
Chrome	47+
Firefox	43+
Safari	9+
Edge	14+
Opera	34+
Internet Explorer	Not supported

Comparison with Other Methods

Method	Purpose
Array.includes() Method	Checks if an array contains a value and handles `NaN` correctly. Returns `true` or `false`.
Array.indexOf() Method	Returns the index of a value in an array or `-1` if not found. Does not handle `NaN`.
Array.some() Method	Checks if at least one element satisfies a given condition.