Checks whether a value is a WHATWG URL.

Works cross-realm/iframe and despite @@toStringTag.

Node.js >= 4 is required. To install, type this at the command line:

npm install isurl

const isURL = require('isurl');

isURL('http://domain/');  //-> false
isURL(new URL('http://domain/'));  //-> true

Optionally, acceptance can be extended to incomplete URL implementations that lack searchParams (which are common in many modern web browsers):

const url = new URL('http://domain/?query');

console.log(url.searchParams);  //-> undefined

isURL.lenient(url);  //-> true