You can even render React components as views on the server in Express, I was shocked how easy it was having used both React as a SPA and Jade views in Express.

You can even render React components as views on the server in Express, I was shocked how easy it was having used both React as a SPA and Jade views in Express. That seems like hands-down the best way to mix server rendered HTML with SPAs, especially if you have to support fallback to pure server rendering.