class Counter extends React.Component {

  constructor(){

    super();

    this.state = {

      count: 0

    };

  }

​

  handleClickMe(e) { //Oops what's wrong? :O

    let newCount = this.state.count + 1;

    this.setState({

      count: newCount

    });

  }

​

  render() {

    return (

      <div>Count: {this.state.count}

        <br/>

        <button onClick={this.handleClickMe}>Increase me</button>

      </div>

    );

  }

}

​

let appEl = document.getElementById('app');

ReactDOM.render(<Counter />, appEl);