Pluralsight React.js: Getting Started - module 2

class Button extends React.Component {


handleClick = () => {
this.props.onClickFn(this.props.incrementValue);
};
 render () {
            return(           
<button onClick={this.handleClick}>
+{this.props.incrementValue}</button>
            );
          }
};

//this class will be used 4to print the result to the screen 
class Result extends React.Component {

 render () {
            return(           
             <div>  er
             {this.props.counter}
              </div>
            );
          }
};

class App extends React.Component {
state = {counter:0};

//this will be used to incrment it will be passed to the btn class
incrementCounter = (incrementValue) => {
this.setState((prevState) => ({
  counter: prevState.counter + incrementValue
}));
};

 render () {
            return(   
              <div>
                <Button incrementValue={1}  onClickFn={this.incrementCounter}/>
                <Button incrementValue={5}  onClickFn={this.incrementCounter}/>
                <Button incrementValue={10}  onClickFn={this.incrementCounter}/>
               <Result counter={this.state.counter} />
               
              </div>
            );
          }
};


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