雑な Firebase Twitter login

auth.js

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

//export default Object.assign({}, {
//  apiKey: process.env.MIX_FIREBASE_API_KEY,
//  authDomain: process.env.MIX_FIREBASE_AUTH_DOMAIN,
//});
// ↑は config/firebase の内容
import firebaseCofnig from '../config/firebase';

export default class Auth {

  constructor() {
    this.firebase = firebase.initializeApp(firebaseCofnig);
    this.provider = new firebase.auth.TwitterAuthProvider();
    this.provider.setCustomParameters({
      'lang': 'ja'
    });
  }

  login() {
    return this.firebase.auth().signInWithPopup(this.provider)
      .then(result => {
        return result;
      }).catch(error => {
        console.log(error);
      });
  }

  logout() {
    firebase.auth().signOut()
      .then(result => {
        console.log('logout.');
      })
      .catch(error => {
        console.log(error);
      });
  }
}