Code cleanup

Our handleSubmit function is getting a little long and difficult to follow. Let's do some reorganization before we move on.

We'll start by moving everything after the initial if statement inside a separate function, called login(), for simplicity:

login() {
  firebase
    .auth()
    .signInWithEmailAndPassword(this.state.email, this.state.password)
    .then(res => {
      console.log(res);
    })
    .catch(err => {
      if (err.code === 'auth/user-not-found') {
        this.signup();
      } else {
        this.setState({ error: 'Error logging in.' });
      }
    });
}

Then, our handleSubmit becomes much smaller:

handleSubmit = event => {
  event.preventDefault();
  this.setState({ error: '' });
  if (this.state.email && this.state.password) {
    this.login();
  } else {
    this.setState({ error: 'Please fill in both fields.' });
  }
};

It's much easier to read and follow now.