Adds "dark" class to the Whatsapp Web document to enable its native dark theme
// ==UserScript==
// @name Whatsapp Native Dark Theme
// @namespace http://web.whatsapp.com/
// @version 1.00
// @description Adds "dark" class to the Whatsapp Web document to enable its native dark theme
// @author Jair Jaramillo
// @match *://web.whatsapp.com/*
// @grant none
// @run-at document-end
// ==/UserScript==
window.addEventListener ("load", pageFullyLoaded);
function pageFullyLoaded () {
document.getElementsByTagName("body")[0].classList.add('dark');
}