const alert = await alertController.create({...});
  await alert.present();

const componentOnReady = (el, callback) => {
  if (el.componentOnReady) {
    el.componentOnReady().then(callback);
  }
  else {
    callback();
  }
};

const createOverlay = (tagName, opts) => {
  /* tslint:disable-next-line */
  if (typeof customElements !== 'undefined') {
    return customElements.whenDefined(tagName).then(() => {
      const element = document.createElement(tagName);
      element.classList.add('overlay-hidden');
      // convert the passed in overlay options into props
      // that get passed down into the new overlay
      Object.assign(element, opts);
      // append the overlay element to the document body
      getAppRoot(document).appendChild(element);
      return new Promise(resolve => componentOnReady(element, resolve));
    });
  }
  return Promise.resolve();
};