Наблюдайте за мутациями элементов

const observeMutations = (element, callback, options) => {
  const observer = new MutationObserver(mutations =>
    mutations.forEach(m => callback(m))
  );
  observer.observe(
    element,
    Object.assign(
      {
        childList: true,
        attributes: true,
        attributeOldValue: true,
        characterData: true,
        characterDataOldValue: true,
        subtree: true,
      },
      options
    )
  );
  return observer;
};

const obs = observeMutations(document, console.log);
// Logs all mutations that happen on the page
obs.disconnect();
// Disconnects the observer and stops logging mutations on the page