clojure.set/map-invert

functionsince v0.0-927 clojure.set/map-invertEdit
(map-invert m)

Source docstring:
Returns the map with the vals mapped to the keys.
Source code @ clojurescript:src/main/cljs/clojure/set.cljs
(defn map-invert
  [m]
  (persistent!
    (reduce-kv (fn [m k v] (assoc! m v k))
      (transient {})
      m)))