function App (){
  const [count, setCount] = React.useState(0);

  React.useEffect(() => {
    console.log('render');
  })
  
  return (
    <div>
      <button type="button" onClick={() => setCount(count + 1)}>
        Count is: { count }
      </button>
    </div>
  )
}

const app = document.querySelector('#app');
const root = ReactDOM.createRoot(app);
root.render(<App />);