pokemon.trade/app/javascript/packs/react-app/routes.js

import React from 'react';
import {BrowserRouter as Router, Route} from 'react-router-dom';

import LandingPage from './components/landing_page';

const App = props => (
  <Router>
    <div>
      <Route exact path="/" component={LandingPage} />
    </div>
  </Router>
);

export default App;