db.js

import firebase from './index'

const db = firebase.firestore()

export default db

index.js

import firebase from '@firebase/app'
import '@firebase/auth'
require('@firebase/firestore')

firebase.initializeApp({
  apiKey: 'AIzaSyBj-SRiWTPBU_au0OfdklVxCBKjVRqIH5w',
  authDomain: 'event-3b891.firebaseapp.com',
  databaseURL: 'https://event-3b891.firebaseio.com',
  projectId: 'event-3b891',
  storageBucket: 'event-3b891.appspot.com',
  messagingSenderId: '378165986536'
})

export default firebase