Embedded Youtube videos to iframe-based Youtube videos

yfr.js

// ==UserScript==
// @name         YouTube Flash Player Replacer
// @namespace    http://0xF.kr/script/
// @version      0.1
// @description  try to take over the world!
// @author       JiminP
// @match        https://namu.wiki/w/*
// @grant        none
// ==/UserScript==
/* jshint -W097 */
'use strict';

// Your code here...
// <iframe width="420" height="315" src="https://www.youtube.com/embed/VEAy700YGuU" frameborder="0" allowfullscreen></iframe>
var embed_regex = /(?:[\/.]|^)youtube\.[^\/]+\/v\/([A-Za-z0-9_\-]{11})/i;

var assign_nonempty = function(f, t, n){
    if(f.hasAttribute(n)) t.setAttribute(n, f.getAttribute(n));
};

var truthy = function(v){
    if(!v) return false;
    if(v === 'false' || v === 'False' || v === 'FALSE') return false;
    if(v === '0') return false;
    return true;
};


window.addEventListener('load', function(){
    var replaced = [];
    [].forEach.call(window.document.getElementsByTagName('object'), function(root){
        var children = [].slice.call(root.children),
            params = {};
        var old_video_url, matches,
            new_video_url = "";
        var new_video_elem = null;
        
        children.forEach(function(param){
            if(param.tagName.toUpperCase() === "PARAM")
                params[param.name] = param.value;
        });
        
        if(!('movie' in params)) return;
        old_video_url = params['movie'];
        if(old_video_url.indexOf("youtube.") === -1) return;
        
        matches = embed_regex.exec(old_video_url);
        if(!matches) return;
        
        new_video_url = "https://www.youtube.com/embed/" + matches[1];
        
        new_video_elem = window.document.createElement('iframe');
        new_video_elem.src = new_video_url;
        new_video_elem.setAttribute('frameborder', '0');
        
        assign_nonempty(root, new_video_elem, 'width');
        assign_nonempty(root, new_video_elem, 'height');
        
        if(truthy(params['allowFullScreen']))
            new_video_elem.setAttribute('allowfullscreen', 'true');
        
        root.parentNode.insertBefore(new_video_elem, root.nextSibling);
        root.parentNode.removeChild(root);
        
        replaced.push(matches[1]);
    });
    [].forEach.call(window.document.getElementsByTagName('embed'), function(root){
        var old_video_url, matches,
            new_video_url = "";
        var new_video_elem = null;
        
        if(!('src' in root)) return;
        
        old_video_url = root.src;
        if(old_video_url.indexOf("youtube.") === -1) return;
        
        matches = embed_regex.exec(old_video_url);
        if(!matches) return;
        
        new_video_url = "https://www.youtube.com/embed/" + matches[1];
        
        new_video_elem = window.document.createElement('iframe');
        new_video_elem.src = new_video_url;
        new_video_elem.setAttribute('frameborder', '0');
        
        assign_nonempty(root, new_video_elem, 'width');
        assign_nonempty(root, new_video_elem, 'height');
        assign_nonempty(root, new_video_elem, 'allowfullscreen');
        
        root.parentNode.insertBefore(new_video_elem, root.nextSibling);
        root.parentNode.removeChild(root);
        
        replaced.push(matches[1]);
    });
    replaced.length && console.info(replaced.length+" YouTube video"+(replaced.length==1 ? " was" : "s were")+" replaced from Flash-based to HTML5-based.");
});