myFirstTestWithReact.js

class Button extends React.Component{
	state = { counter: 0 };
  
  handleClick = () => {
  	this.setState((prevState) => ({
    	counter: prevState.counter + 1
    }));
  };
  
  render(){
  	return (
    	<button onClick={this.handleClick}>
        {this.state.counter}
      </button>
    );
  }
}

ReactDOM.render(<Button />, mountNode);