import React from "react";
import ReactDOM from "react-dom";
class App extends React.Component {

  constructor(){
    super();
    this.state = {text: "click to change"};


  }

  ouch = () => {
    this.setState({text: "woot"});
  }


  render() {
    return <div>
      <p>{this.state.text}</p>
      <button onClick={this.ouch}>Yo</button>
    </div>
  }

}
var app = document.getElementById('app');
ReactDOM.render(<App />, app);