How to check if all items in an array are equal in JavaScript

In this Article we will go through how to check if all items in an array are equal only using single line of code in JavaScript. This is a one-line JavaScript code snippet that uses one of the most popular ES6 features => Arrow Function.

Let's define this short function:

const areEqual = arr => arr.length > 0 && arr.every(item => item === arr[0]);

const areEqual = arr => new Set(arr).size === 1;

areEqual([1, 2, 3, 4]);                 // false
areEqual(['hello', 'hello', 'hello']);  // true