Login.vue

<script>
  import firebase from 'firebase'

  export default {
    name: 'login',
    data: function() {
      return {
        email: '',
        password: ''
      }
    },
    methods: {
      login () {
        firebase.auth().signInWithEmailAndPassword(this.email, this.password).then((user) => {
          this.$router.replace('/comics')
        }).catch((err) => {
          alert(err.message)
        })
      }
    }
  }
</script>