React + Firebase - Persistent Auth

Login.js

import React, { Component } from 'react';
import firebase from 'firebase';
import { browserHistory } from 'react-router';
import { routeCodes } from 'routes';
import FormLogin from 'components/form/Form.login';

export default class Login extends Component {

    constructor (props) {
        super(props);
        this.state = { error: {} };
        this.onLogin = this.onLogin.bind(this);
    }
    
    reset () {
        return new Promise(resolve => this.setState({ error: {} }, () => resolve()));
    }

    onLogin ({ email, password }) {
        this.reset()
            .then(() => firebase.auth().signInWithEmailAndPassword(email, password))
            .then(() => browserHistory.push(routeCodes.ADMIN))
            .catch(error => this.setState({ error }));
    }

    render () {
        return (
            <article>
                <FormLogin
                    onSubmit={ this.onLogin }
                    error={ this.state.error } />
            </article>
        );
    }
}