facenovel/app/views/static_pages/root.html.erb

<% if logged_in? %>
  <script type="text/javascript">
      window.currentUser = <%= render(
        "api/users/user.json.jbuilder",
        user: current_user
      ).html_safe %>
  </script>
<% end %>

<main id="root">React is BROKEN yo</main>