I have a similar feeling about Vuex in the Vue world. Trying to recreate the Elm architecture without Elm ends up being a bit awkward. It's not just immutability and pure functions, as others have noted, it's even more down to a lack in JavaScript of algebraic data types (tagged unions) and pattern matching. Without those, and other Elm language features, you end up getting some quite obscure looking and verbose code and "magic" strings all of which is difficult to type-check (e.g. Flow). Good old-fashioned singleton state modules work better for me.