How to check if a flat array has duplicate values in JavaScript

In this Article we will go through how to check if a flat array has duplicate values 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 hasDuplicateValues = arr => new Set(arr).size !== arr.length;

hasDuplicateValues(['h', 'e', 'l', 'l', 'o']);      // true
hasDuplicateValues(['w', 'o', 'r', 'd']);           // false