How to check if a url is absolute in JavaScript

In this Article we will go through how to check if a url is absolute 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 isAbsoluteUrl = url => /^[a-z][a-z0-9+.-]*:/.test(url);

isAbsoluteUrl('https://1loc.dev');          // true
isAbsoluteUrl('https://1loc.dev/foo/bar');  // true
isAbsoluteUrl('1loc.dev');                  // false
isAbsoluteUrl('//1loc.dev');                // false