Authentication with Firebase

import firebase from 'firebase'
let config = {
  apiKey: "YOUR_API_KEY",
  authDomain: "YOUR_PROJECT_ID.firebaseapp.com",
  databaseURL: "https://YOUR_PROJECT_ID.firebaseio.com",
  projectId: "YOUR_PROJECT_ID",
  storageBucket: "YOUR_PROJECT_ID.appspot.com",
  messagingSenderId: "YOUR_MESSAGING_SEND_ID"
};
let app;
firebase.initializeApp(firebase_config)
firebase.auth().onAuthStateChanged(function(user) {
  if (!app) {
    app = new Vue({
    })
  }
});

//----------- signup & login -------------- 
firebase.auth().createUserWithEmailAndPassword(email, password)
firebase.auth().signInWithEmailAndPassword(email, password)
//---------------------------------------------------------
https://medium.com/@anas.mammeri/vue-2-firebase-how-to-build-a-vue-app-with-firebase-authentication-system-in-15-minutes-fdce6f289c3c