Find all custom elements on the page

getAllCustomElements.js

  const allCustomElements = [];

  function isCustomElement(el) {
    const isAttr = el.getAttribute('is');
    // Check for <super-button> and <button is="super-button">.
    return el.localName.includes('-') || isAttr && isAttr.includes('-');
  }

  function findAllCustomElements(nodes) {
    for (let i = 0, el; el = nodes[i]; ++i) {
      if (isCustomElement(el)) {
        allCustomElements.push(el);
      }
      // If the element has shadow DOM, dig deeper.
      if (el.shadowRoot) {
        findAllCustomElements(el.shadowRoot.querySelectorAll('*'));
      }
    }
  }

  findAllCustomElements(document.querySelectorAll('*'));

  console.log(allCustomElements);