In my opinion mutable state is most often better than immutable state. In JavaScript, that is, I have a different opinion on the JVM. The important point is th

In my opinion mutable state is most often better than immutable state. In JavaScript, that is, I have a different opinion on the JVM. The important point is that the state is _serializable_, meaning it doesn't contain side-effects. That also means NetworkRequests must be replayable. If your state is serializable, you get immutability out of the box by serializing everthing to JSON and back again.