react.html

'use strict';

// エレメントの作成
const e = React.createElement;

class LikeButton extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      liked: false,
      count: 0
    };
  }

  render() {
    return e(
      'button', {
        onClick: () => this.setState({
          liked: true,
          count: this.state.count + 1
        })
      },
      `いいね ${this.state.count}`
    );
  }
}

const domContainer = document.querySelector('#like_button_container');
ReactDOM.render(e(LikeButton), domContainer);