updateSubtreeComplete

updateSubtreeComplete.js

class MyElement extends LitElement {
  
  // Promise that will resolve when the entire subtree of the element's `renderRoot` has finished updating/rendering.
  get updateSubtreeComplete() {
      async function awaitSubtree(el) {
        await el.updateComplete;
        const clients = el.renderRoot!.querySelectorAll('*');
        await Promise.all(Array.from(clients).map((e) =>
          e.updateSubtreeComplete || awaitSubtree(e as UpdatingElement)));
      }
      return awaitSubtree(this);
    }
  }
  
}