server.js

// Server Side Rendering based on routes matched by React-router.
app.use((req, res) => {
  match({ routes, location: req.url }, (err, redirectLocation, renderProps) => {
    if (err) {
      return res.status(500).end('Internal server error');
    }

    if (!renderProps) {
      return res.status(404).end('Not found!');
    }

    const initialState = { posts: [], post: {} };

    const store = configureStore(initialState);

    fetchComponentData(store.dispatch, renderProps.components, renderProps.params)
      .then(() => {
        const initialView = renderToString(
          <Provider store={store}>
            <RouterContext {...renderProps} />
          </Provider>
        );
        const finalState = store.getState();

        res.status(200).end(renderFullPage(initialView, finalState));
      })
      .catch(() => {
        res.end(renderFullPage('Error', {}));
      });
  });
});