function Button(props) {
  const handleClick = () => props.onClickFunction(props.increment)

  return (
    <button onClick={ handleClick }>
      +{props.increment}
    </button>
    )
}

function Display(props) {
  return (
    <div>{props.message}</div>
  )
}

function App() {
  const [ counter, setCounter ] = useState(0)
  const incrementCounter = ( incrementValue ) => setCounter( counter + incrementValue)


  return (
    <div>
      <Button onClickFunction={incrementCounter} increment={1} />
      <Button onClickFunction={incrementCounter} increment={5} />
      <Button onClickFunction={incrementCounter} increment={10} />
      <Button onClickFunction={incrementCounter} increment={100} />
      <Display message={ counter }/>
    </div>
  )
}


ReactDOM.render(
  <App />,
  document.getElementById('mountNode')
)