rsnext/examples/with-firebase-authentication/utils/auth/initFirebase.js

import firebase from 'firebase/app'
import 'firebase/auth'

const config = {
  apiKey: process.env.FIREBASE_PUBLIC_API_KEY,
  authDomain: process.env.FIREBASE_AUTH_DOMAIN,
  databaseURL: process.env.FIREBASE_DATABASE_URL,
  projectId: process.env.FIREBASE_PROJECT_ID,
}

export default function initFirebase() {
  if (!firebase.apps.length) {
    firebase.initializeApp(config)
  }
}