Function createCustomElementClass

src/custom-element.js:93–114

(win, elementConnectedCallback)

 * @return {typeof AmpElement} The custom element class.
 */
export function createCustomElementClass(win, elementConnectedCallback) {
  const BaseCustomElement = /** @type {typeof HTMLElement} */ (
    createBaseCustomElementClass(win, elementConnectedCallback)
  );
  // It's necessary to create a subclass, because the same "base" class cannot
  // be registered to multiple custom elements.
  class CustomAmpElement extends BaseCustomElement {
    /**
     * adoptedCallback is only called when using a Native implementation of Custom Elements V1.
     * Our polyfill does not call this method.
     */
    adoptedCallback() {
      // Work around an issue with Firefox changing the prototype of our
      // already constructed element to the new document's HTMLElement.
      if (Object.getPrototypeOf(this) !== customAmpElementProto) {
        Object.setPrototypeOf(this, customAmpElementProto);
      }
    }
  }
  const customAmpElementProto = CustomAmpElement.prototype;
  return /** @type {typeof AmpElement} */ (CustomAmpElement);
}

/**
 * Creates a base custom element class.