Back to authentication

Since we expect an error to be returned (since we haven't signed up with any email and password combination), we can leave our then statement blank, but add a console log to our catch statement:

handleSubmit = (event) => {
  event.preventDefault();
  this.setState({ error: '' });
  if (this.state.email && this.state.password) {
    firebase.auth().signInWithEmailAndPassword(this.state.email, this.state.password)
      .then(res => { console.log(res); })
      .catch(err => { console.log(err); })
  } else {
    this.setState({ error: 'Please fill in both fields.' });
  }
}

Submit your form, and you should be returned the following error:

{code: "auth/user-not-found", message: "There is no user record corresponding to this identifier. The user may have been deleted."}

Great! This is exactly the error we wanted. This is the code we'll check for, before initiating the signup process. For now, we'll assume that all the other errors are due to an incorrect password:

handleSubmit = (event) => {
  event.preventDefault();
  this.setState({ error: '' });
  if (this.state.email && this.state.password) {
    firebase.auth().signInWithEmailAndPassword(this.state.email, 
     this.state.password)
      .then(res => { console.log(res); })
      .catch(err => { 
        if (error.code === 'auth/user-not-found') { 
          // Sign up here.
        } else { 
          this.setState({ error: 'Error logging in.' }) ;
        }
      })
 } else {
   this.setState({ error: 'Please fill in both fields.' });
 }
}