How to Check if an Element Exists in an Array in JavaScript ?

In JavaScript, you can check if an element exists in an array using various methods, such as indexOf(), includes(), find(), some(), or Array.prototype.findIndex().

Here’s how you can achieve it using these methods:

Using indexOf() method

The indexOf() method returns the first index at which a given element can be found in the array, or -1 if it is not present.

const array = [1, 2, 3, 4, 5];
const element = 3;
 // Checks if element exists
const exists = array.indexOf(element) !== -1;
console.log(exists); // Output: true

Using includes() method

The includes() method returns a boolean indicating whether an array includes a certain value among its entries.

const array = [1, 2, 3, 4, 5];
const element = 3;
 // Checks if element exists
const exists = array.includes(element);
console.log(exists); // Output: true

Using find() method

The find() method returns the value of the first element in the array that satisfies the provided testing function.

const array = [1, 2, 3, 4, 5];
const element = 3;
// Checks if element exists
const exists = array.find(item => item === element) !== undefined; 
console.log(exists); // Output: true

Using some() method

The some() method tests whether at least one element in the array passes the test implemented by the provided function.

const array = [1, 2, 3, 4, 5];
const element = 3;
// Checks if element exists
const exists = array.some(item => item === element); 
console.log(exists); // Output: true

Using Array.prototype.findIndex() method

The findIndex() method returns the index of the first element in the array that satisfies the provided testing function. Otherwise, it returns -1.

const array = [1, 2, 3, 4, 5];
const element = 3;
// Checks if element exists
const exists = array.findIndex(item => item === element) !== -1; 
console.log(exists); // Output: true