function UnmemorizedComponent({myProp}) {
  const refConunt = React.useRef(0)
  refConunt.current ++
  
  return (
    <div>{myProp}, count = {refConunt.current}</div>
  );
}

const MemorizedComponent = React.memo(UnmemorizedComponent)

function App() {
  const [buttonState, setButtonState] = React.useState(false)
  const handleClickButton = () => {
    setButtonState(!buttonState)
  }
   
  return (
    <div>
      <button onClick={handleClickButton}>click</button>
      <UnmemorizedComponent myProp={"UnmemorizedComponent"}/>
      <MemorizedComponent myProp={"MemorizedComponent"}/>
    </div>
  )
}

ReactDOM.render(
  <App />, 
  document.getElementById("root")
);