ReactJS - Reactjs orientado a objetos

import React from "react";

export default class App extends React.Component {

  constructor(props) {

    super(props);

    this.state = {

      initialValue: 1

    }

  }

  changeState() {

    this.setState({newValue: 2});

  }

  render() {

    return (

      <React.Fragment>

        <p onClick={ () => changeState() }>Hello World!!</p>

      </React.Fragment>

    );

  }

}