Script to convert old youtube (object) embeds to new youtube (iframe) embeds

retube.bookmarklet.js

Array.from(document.querySelectorAll('param[name="src"][value*="youtube"]')).forEach(function(srcEl) {
  var src = srcEl.getAttribute('value');
  if (!src) {
    return;
  }
  var objectEl = srcEl.parentElement;
  if (!objectEl) {
    return;
  }
  var container = objectEl.parentElement;
  if (!container) {
    return;
  }
  var width = objectEl.getAttribute('width') || '420';
  var height = objectEl.getAttribute('height') || '336';
  src = 'https://www.youtube.com/embed/' + src.split('/').pop().split('?').shift();
  var iframe = document.createElement('iframe');
  iframe.setAttribute('width', width);
  iframe.setAttribute('height', height);
  iframe.setAttribute('src', src);
  iframe.setAttribute('frameborder', '0');
  iframe.setAttribute('allowfullscreen', 'allowfullscreen');
  container.insertBefore(iframe, objectEl);
  container.removeChild(objectEl);
});