[phyrex]

If you're using pure functions then you'd likely profit from clojure's data structures, as they're much cheaper to copy and modify than javascript's native structures. Of course you could use something like ImmutableJS or Immer, but then you're putting yourself at odds with the rest of the JS ecosystem and built-in functions and you have to transform values back and forth. This gets a lot easier with Clojure(script) (even though there's obviously still some casting back and forth when you're going outside the CLJs ecosystem)