js.js

// ==UserScript==
// @name         Remove GitHub dark bar
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        https://github.com/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';
    document.getElementsByClassName('header-dark')[0].className =
    document.getElementsByClassName('header-dark')[0].className
    .replace(new RegExp('(?:^|\\s)'+ 'header-dark' + '(?:\\s|$)'), ' ');
    // Your code here...
})();