Adds a link on youtube pages to download the video via proxy server (YouTube-Downloader)

ytdl.user.js

// ==UserScript==
// @name            Youtube Downloader
// @description     Adds a link on youtube pages to download the video via proxy server.
//
// @author	        Sepehr Lajevardi <[email protected]> modded by ewwink
// @namespace       http://github.com/sepehr
//
// @version         1.1
// @license         GPLv3 - http://www.gnu.org/licenses/gpl-3.0.txt
// @copyright       Copyright (C) 2013, by Sepehr Lajevardi <[email protected]>
//
// @include         http*://*.youtube.com/*
// @grant           none
// ==/UserScript==
/**
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
// ------------------------------------------------------------------------
// Helpers
// ------------------------------------------------------------------------
window.location.getParam = function(name) {
  name = name.replace(/[\[]/, "\\\[").replace(/[\]]/, "\\\]");

  var regex = new RegExp("[\\?&]" + name + "=([^&#]*)"),
    result = regex.exec(window.location.search);

  if (result == null) {
    return false;
  }

  return decodeURIComponent(result[1].replace(/\+/g, ' '));
};

// ------------------------------------------------------------------------
// @ts-check

/**
 * Youtube downloader.
 *
 * @see http://wiki.greasespot.net/API_reference
 * @see http://wiki.greasespot.net/Metadata_Block
 */

function YoutubeDownloader() {

  var wrapper = document.getElementById('watch7-subscription-container'),
    btn = document.createElement('a'),
    vid = window.location.getParam('v'),
    style = document.createElement('style'),
    head = document.getElementsByTagName('head')[0],
    // Update this to point to your own installation:
    link = 'http://UPDATE_THIS_IN_CODE.com/getvideo.php?videoid=' + vid + '&type=Download';

  if (wrapper && vid) {
    // Assemble the button:
    btn.type = 'button';
    btn.setAttribute('href', link);
    btn.setAttribute('role', 'button');
    btn.setAttribute('style', 'line-height:inherit;height:23px;border-color:#b3b3b3 !important');
    btn.setAttribute('class', 'yt-uix-subscription-button yt-uix-button yt-uix-button-subscribe-branded');

    // Child elements:
    btn.innerHTML = '<span class="yt-uix-button-icon-wrapper" style="background:#b3b3b3;border-color:#b3b3b3">\
			<img class="guide-management-plus-icon" src="//s.ytimg.com/yts/img/pixel-vfl3z5WfW.gif">\
			<span class="yt-uix-button-valign"></span>\
		</span>\
		<span class="yt-uix-button-content">\
			<span class="subscribe-label">Download</span>\
			<span class="unsubscribe-label"></span>\
		</span>';

    // Append it:
    wrapper.appendChild(btn);

    // Style:
    style.type = 'text/css';
    style.innerHTML = '#watch7-subscription-container .yt-uix-button-subscription-container { float: left !important; margin-left: 10px !important; }';
    head.appendChild(style);
  }
}

var fireOnHashChangesToo = true;
var oldWatchCount = document.getElementsByClassName('watch-view-count')[0].innerHTML;
var pageURLCheckTimer = setInterval(function() {
  var newWatchCount = document.getElementsByClassName('watch-view-count')[0].innerHTML;
  if (this.lastPathStr !== location.pathname || this.lastQueryStr !== location.search || (fireOnHashChangesToo && this.lastHashStr !== location.hash || oldWatchCount != newWatchCount)) {
    oldWatchCount = newWatchCount;
    this.lastPathStr = location.pathname;
    this.lastQueryStr = location.search;
    this.lastHashStr = location.hash;
    console.log('page changed');
    YoutubeDownloader();
  }
}, 500);