JavaScript - check if array contains value

In this article, we would like to show you how to check if array contains value using JavaScript.

Quick solution:

// ONLINE-RUNNER:browser;

const array = ['a', 'b', 'c'];

console.log(array.indexOf('b') !== -1);  // true

Hint: this solution works even in older web browsers and Node.js.

or:

// ONLINE-RUNNER:browser;

const array = ['a', 'b', 'c'];

console.log(array.includes('b'));  // true

Warning: Array includes() was introduced in ES6 (around 2016).

Practical examples

1. Array indexOf() method

In this example, we use includes() method to check if letters array contains specific characters.

// ONLINE-RUNNER:browser;

const letters = ['a', 'b', 'c'];

console.log(letters.indexOf('b') !== -1);  // true
console.log(letters.indexOf('x') !== -1);  // false

with numbers:

// ONLINE-RUNNER:browser;

const numbers = [1, 2, 3];

console.log(numbers.indexOf(1) !== -1);  // true
console.log(numbers.indexOf(4) !== -1);  // false

2. Array includes() method

In this example, we use includes() method to check if letters array contains specific characters.

// ONLINE-RUNNER:browser;

const letters = ['a', 'b', 'c'];

console.log(letters.includes('b'));  // true
console.log(letters.includes('x'));  // false

with numbers:

// ONLINE-RUNNER:browser;

const numbers = [1, 2, 3];

console.log(numbers.includes(1));  // true
console.log(numbers.includes(4));  // false

Reusable function

In this section, you can find a function that works in older and modern web browsers or Node.js.

// ONLINE-RUNNER:browser;

const containsItem = (array, item) => array.indexOf(item) !== -1;


// Usage example:

const letters = ['a', 'b', 'c'];

console.log(containsItem(letters, 'b'));  // true
console.log(containsItem(letters, 'x'));  // false

References

1. Array.prototype.includes() - JavaScript | MDN