Hi, shameless plug: another (typed) immutable data structure library, https://github.com/gcanti/tcomb. Main features:

- works with regular objects and arrays - runtime type checks - easy debugging with Chrome DevTools - immutability and immutability helpers - runtime type introspection - easy JSON serialization / deseralization - pattern matching

Also https://github.com/gcanti/redux-tcomb (Immutable and type-checked state and actions for Redux)