I do really wish JS had native immutables with structural sharing, though.
- You have experience with Lisp dialects (even better, Clojure specifically).
In this case, you know the language semantics but not the application of in this domain. The core concepts are so simple, and there is so much material out there covering it, that picking this up should be easy.
- You have experience with modern reactive architectures in any language and an understanding to structure application state atoms.
In this case the concepts you learned will largely prevail and you will be left learning the language semantics. While Clojure has an enormous core library, you can do a lot with only a very rudimentary knowledge of the language.
Also, what you aim for will probably make a difference. Reagent and the hiccup style is incredibly easy to pick up, and re-frame supplies a very nice state manager. Om and Om/Next are probably more difficult to pick up, and at least in the case of Om, probably not worth it now. Om/Next seems to be an attempt at replicating an entire React/Relay or Falcor/GraphQL stack in Clojure/ClojureScript, and at this point it is dubious what size of an application you need to develop to break even on the architecture and complexity costs.