onEnter_async_redux_action.js

// Most of the time you can do data loading in react-router's onEnter/onLeave hooks, which support async operations. If you're using Redux or some other flux implementation, you can dispatch a loading() action, perform your data fetching, and then dispatch a loaded() action once the data's ready.

function fetchData(nextState, replace, done) {
  store.dispatch(loading());
  doAsyncThing().then(() => {
    store.dispatch(loaded());
    done();
  });
}

<Route
  path="/whatev"
  onEnter={ fetchData }
  component={ Whatev }
/>

// The Whatev component can then use connect decorator from react-redux to pipe in the data as props.