Login (A class component)

login.js

class Login extends React.Component {
  constructor(props) {
    super(props);
    this.handleChange = this.handleChange.bind(this);
    this.handleLogIn = this.handleLogIn.bind(this);
    this.state = {username: ''};
  }

  render() {
    return (
      <Dialog title="Login now"
              message="Get more superpowers for free">
        <input value={this.state.username}
               onChange={this.handleChange} />

        <button onClick={this.handleLogIn}>
          Log Me In!
        </button>
      </Dialog>
    );
  }
  handleChange(e) {
    this.setState({username: e.target.value});
  }

  handleLogIn() {
    alert(`Welcome back, ${this.state.username}!`);
  }
}