ionic-framework/vue/src/api-utils.ts

import { HTMLStencilElement } from '@ionic/core';

// A proxy method that initializes the controller and calls requested method
export function proxyMethod(tag: string, method: string, ...opts: any[]): Promise<any> {
  return initController(tag).then((ctrl: any) => ctrl[method].apply(ctrl, opts));
}

// Initialize an Ionic controller and append it to DOM
export function initController(tag: string): Promise<HTMLStencilElement> {
  let element = document.querySelector(tag) as HTMLElement;

  if (!element) {
    element = document.body.appendChild(document.createElement(tag));
  }

  return (element as HTMLStencilElement).componentOnReady();
}