// ... previous imports
import { BrowserRouter as Router, Link, Route } from 'react-router-dom';

function Home() {
  return <h2>Home</h2>;
}

function Notes() {
  return <h2>Notes</h2>;
}

function Todos() {
  return <h2>Todos</h2>;
}

function App() {
  return (
    <Router>
      <div>
        <nav>
          <ul>
            <li>
              <Link to="/">Home</Link>
            </li>
            <li>
              <Link to="/notes/">Notes</Link>
            </li>
            <li>
              <Link to="/todos/">Todos</Link>
            </li>
          </ul>
        </nav>

        <Route path="/" exact component={Home} />
        <Route path="/notes/" component={Notes} />
        <Route path="/todos/" component={Todos} />
      </div>
    </Router>
  );
}
// ...