Function findCheckedOption

core/src/utils/watch-options.ts:37–52

(node: Node, tagName: string)

 * such as HTMLIonSelectOptionElement.
 */
export const findCheckedOption = <T extends HTMLElement & { value?: any | null }>(node: Node, tagName: string) => {
  /**
   * https://developer.mozilla.org/en-US/docs/Web/API/Node/nodeType
   * The above check ensures "node" is an Element (nodeType 1).
   */
  if (node.nodeType !== 1) {
    return undefined;
  }

  // HTMLElement inherits from Element, so we cast "el" as T.
  const el = node as T;

  const options: T[] = el.tagName === tagName.toUpperCase() ? [el] : Array.from(el.querySelectorAll(tagName));

  return options.find((o: T) => o.value === el.value);
};