Autofocus for all HTML Elements

focus.js

(_ => {
  const target = document.documentElement;

  // config object
  const config = {
    attributes: true,
    attributeOldValue: true,
    characterData: true,
    characterDataOldValue: true,
    childList: true,
    subtree: true
  };

  // subscriber function
  function subscriber(mutations) {
    mutations.forEach(mutation => {
      let { target } = mutation;

      if (
        target.nodeType === Node.ELEMENT_NODE &&
        target.hasAttribute("focus")
      ) {
        target.focus();
      }
    });
  }

  // instantiating observer
  const observer = new MutationObserver(subscriber);

  // observing target
  observer.observe(target, config);
})();