functionsince v0.0-2411 clojure.core/updateEdit
(update m k f)
(update m k f x)
(update m k f x y)
(update m k f x y z)
(update m k f x y z & more)

Source docstring:
'Updates' a value in an associative structure, where k is a
key and f is a function that will take the old value
and any supplied args and return the new value, and returns a new
structure.  If the key does not exist, nil is passed as the old value.
Source code @ clojurescript:src/main/cljs/cljs/core.cljs
(defn update
  ([m k f]
   (assoc m k (f (get m k))))
  ([m k f x]
   (assoc m k (f (get m k) x)))
  ([m k f x y]
   (assoc m k (f (get m k) x y)))
  ([m k f x y z]
   (assoc m k (f (get m k) x y z)))
  ([m k f x y z & more]
   (assoc m k (apply f (get m k) x y z more))))