App.js

import React, { Component } from 'react';

class App extends Component {
  constructor(props) {
    super(props);
    this.state = {
      username: '',
      password: '',
      passwordConfirmation: '',
      email: '',
      errors: []
    };
    this.validateUsernameOnBlur = this.validateUsernameOnBlur.bind(this);
  }
  displayForm() {
    return (
      <div>
        Username: <input type="text" onBlur={this.validateUsernameOnBlur} /><br />
        Password: <input type="text" /><br />
        Password Confirmation: <input type="text" /><br />
        Email: <input type="text" /><br />
        <br />
        <button onClick={this.submitForm}>Submit</button>
      </div>
    );
  }
  validateUsernameOnBlur(event) {
    console.log("I should validate whatever is in ", event.target.value);
    this.setState();
  }
  submitForm(event) {
    console.log("Submitting the form now...");
    console.log(event);
  }
  render() {
    return (
      <div className="App">
        Create Account
      <hr />
        {this.displayForm()}
      </div>
    )
  }

}

export default App;