Forces the transparent player on YouTube for testing purposes

YouTube transparent player.user.js

// ==UserScript==
// @version     1
// @name        YouTube transparent player
// @namespace   none
// @description Forces the transparent player on YouTube for testing purposes
// @match       *://www.youtube.com/*
// @run-at      document-start
// @grant       none
// @noframes
// ==/UserScript==
(function () {
    'use strict';
    function switchPlayer(event) {
        var ytConfig,
            script = 'https://s.ytimg.com/yts/jsbin/html5player-new-vflkiLxkD/html5player-new.js',
            style = 'https://s.ytimg.com/yts/cssbin/www-player-new-vfl2ujh_c.css';
        if (event.target.getAttribute('name') === 'html5player/html5player' && event.target.src !== script) {
            event.preventDefault();
            event.stopPropagation();
        }
        if (event.target.textContent.split('var ytplayer = ytplayer').length > 1) {
            event.preventDefault();
            event.stopPropagation();
            if (window.location.href.split('/watch').length > 1) {
                ytConfig = event.target.textContent.match(/ytplayer\.config = \{([\w\W]*?)\};/)[1];
                window.ytplayer = window.ytplayer || {};
                window.ytplayer.config = JSON.parse('{' + ytConfig + '}');
                window.ytplayer.config.html5 = true;
                window.ytplayer.config.assets.css = style;
                window.ytplayer.config.assets.js = script;
            }
        }
    }
    window.addEventListener('beforescriptexecute', switchPlayer);
    //window.matchMedia = false; //Enable this to allow proper resizing of the player and its contents
}());