How to check if a string contains upper case characters in JavaScript

In this Article we will go through how to check if a string contains upper case characters 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 containsUpperCase = str => str !== str.toLowerCase();

containsUpperCase('Hello World');   // true
containsUpperCase('hello world');   // false