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

In this Article we will go through how to check if a string contains lower 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 containsLowerCase = str => str !== str.toUpperCase();

containsLowerCase('Hello World');   // true
containsLowerCase('HELLO WORLD');   // false