Replaces all YouTube embed URLs

Yoshino.js

// ==UserScript==
// @name Yoshino
// @namespace moe.greydus
// @version 2.28.0
// @description Replaces all YouTube embed URLs
// @match *://*/*
// @exclude-match https://www.youtube.com/*
// ==/UserScript==
var iframe_list = document.querySelectorAll('iframe[src*="www.youtube.com"]');

for(var i = 0; iframe_list.length > 0 && i < iframe_list.length; i++) {
  var iframe = iframe_list[i];

  // Some embeds use the `data-src` attribute
  if(iframe.getAttribute("data-src") != null)
    iframe.setAttribute("data-src", Zadkiel(iframe.getAttribute("data-src")).invidious.url);

  if(iframe.getAttribute("src") != null)
    iframe.setAttribute("src", Zadkiel(iframe.getAttribute("src")).invidious.url);
}

function Zadkiel(youtube_video_url) {
  var youtube_video_url_regexp = /(http(?:s)?:)?\/\/(www\.youtube(?:-nocookie)?\.com)(\/(?:watch\?v=|embed\/))([A-Za-z0-9-_]+)/, _protocol, _domain, _path, _id;

  if(youtube_video_url != undefined) {
    _protocol = ((youtube_video_url.match(youtube_video_url_regexp)[1] != undefined) ? youtube_video_url.match(youtube_video_url_regexp)[1] : "");
    _domain = youtube_video_url.match(youtube_video_url_regexp)[2];
    _path = youtube_video_url.match(youtube_video_url_regexp)[3];
    _id = youtube_video_url.match(youtube_video_url_regexp)[4];

    return {
      id: _id,
      youtube: {
        url: _protocol + "//" + _domain + _path + _id,
        short_url: "https://youtu.be/" + _id
      },
      invidious: {
        url: _protocol + "//invidio.us" + _path + _id
      },
      hooktube: {
        url: _protocol + "//hooktube.com" + _path + _id
      }
    }
  }

  return null;
}