JavaScript – Return an object of all the html tag names and the number of times they appear in the document

unique-dom-elements.js

const uniqueDomElements = () =>
  Array.from(document.querySelectorAll('*')).reduce(
    (obj, { tagName }) => {
      obj[tagName] = obj[tagName] + 1 || 1;
      obj._total += 1;
      return obj;
    },
    { _total: 0 }
  );