function UserGreeting(props) {
  return 
Welcome back!
;
}

function GuestGreeting(props) {
  return 
Please sign up.
;
}

function Greeting(props) {
  const isLoggedIn = props.isLoggedIn;
  if (isLoggedIn) {
    return ;
  }
  return ;
}

ReactDOM.render(
  // Try changing to isLoggedIn={true}:
  ,
  document.getElementById('root')
);