Cleaned up Firebase V8 Lazy Loading Example

firebase_V8_async.js

// firebaseApp replaces import firebase from "firebase/app" (the _only_ named import)
// firebaseAppPromise is the promise that gets awaited immediately to prevent multi-call re-init
let firebaseApp, firebaseAppPromise;
export async function getFirebaseApp() {
  if (!firebaseApp) {
    if (!firebaseAppPromise) firebaseAppPromise = import(/*webpackPreload: true*/ "firebase/app");
    firebaseApp = await firebaseAppPromise;
  }
  return firebaseApp;
}

const config = {
  //...
}

let app, appPromise;
export async function getApp() {
  if (!app) {
    if (!appPromise) appPromise = getFirebaseApp().then(firebase => firebase.initializeApp(config));
    app = await appPromise;
  }
  return app;
}

let auth, authPromise;
export async function getAuth() {
  if (!auth) {
    if (!authPromise) authPromise = [import(/*webpackPreload: true*/ "firebase/auth"), getApp()];
    await authPromise[0]; auth = (await authPromise[1]).auth();
  }
  return auth;
}

let functions, functionsPromise;
export async function getFunctions() {
  if (!functions) {
    if (!functionsPromise) functionsPromise = [
      import(/*webpackPrefetch: true*/ "firebase/functions"), getApp()];
    await functionsPromise[0]; functions = (await functionsPromise[1]).functions();
  }
  return functions;
}

let storage, storagePromise;
export async function getStorage() {
  if (!storage) {
    if (!storagePromise) storagePromise = [
      import(/*webpackPreload: true*/ "firebase/storage"), getApp()];
    await storagePromise[0]; storage = (await storagePromise[1]).storage();
  }
  return storage;
}