Real world usage of distributed software always entails the possibility of network failure. Using a variety of techniques, offline robustness can be maximized.

• Progressive Web Apps - service workers for precaching and offline rendering of the application shell
• Optimized protocols and technology like MQTT and Erlang
• Aggressive local caching and preloading wherever possible - here's a small npm package I wrote. (and here's an article explaining the why and how in more detail.)