volkan-k / YouTube - Always Theater Mode

// ==UserScript==
// @name        YouTube - Always Theater Mode
// @namespace   volkank/youtube/theater
// @description Set the default viewing mode to Theater Mode.
// @include     https://www.youtube.com/*
// @version     1.1
// @grant       unsafeWindow
// @run-at      document-start
// @license     MIT
// @require 	https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.4/jquery.min.js
// @require 	https://cdnjs.cloudflare.com/ajax/libs/js-cookie/2.0.4/js.cookie.min.js
// ==/UserScript==

this.$ = this.jQuery = jQuery.noConflict(true);

function set_wide_on() {
	if (Cookies.get('wide')!=1){
		Cookies.set('wide', 1, { domain: '.youtube.com' , expires: 365 });
		var newPlayer = $('button.ytp-size-button');
		if ( newPlayer.length>0 ) {
			newPlayer[0].click();
		}
	}
}

setInterval(set_wide_on, 1000);