safaribook-aspnet-core5-and-react/QandA/frontend/src/App.tsx

import React from 'react';
import { Header } from './Header';
import './App.css';

function App() {
  return (
    <div className="App">
      <Header />
    </div>
  );
}

class ProblemComponent extends React.Component {
  render() {
    return <div ref="div" />;
  }
}

export default App;