SignUpFormEx.es6

class SignUpForm extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      email: null,
      username: null,
    };
    
    this._change = this._change.bind(this);
    this._validate = this._validate.bind(this);
  }
  
  _change(e) {
    this.setState({
      [e.target.name]: e.target.value
    });
  }
  
  _validate() {
    // Do validations here!
  }
  render() {
    return(
      <form>
        Usernane: <input type='text' name='username' value={this.state.username} onChange={this._change} />
        Email: <input type='email' name='email' value={this.state.email} onChange={this._change} />
        <button onClick={this._validate}>Submit</button>
      </form>
    );
  }
}