React 18로 업그레이드 된 후로 18버전을 쓰려고 한다. 이떄 ReactDOM.render는 지원하지 않기 때문에 주의해서 사용하길! ReactDOM.render를 쓰면 17을 쓰게된당~ ReactDOM.render is no longer supported in React 18. Use createRoot instead. Until you switch to the new API, your app will behave as if it’s running React 17. Learn more: https://reactjs.org/link/switch-to-createroot Before import React from "react"; import ReactDOM from "react-dom"; impor..