gen-uuid.cljs

(defn- generate-uuid []
  (let [pattern "xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx"
        time-api (or js/performance js/Date)
        now (atom (.now time-api))]
    (replace pattern #"[xy]" (fn [char]
                               (let [r (-> (rand)
                                           (* 16)
                                           (+ @now)
                                           (rem 16)
                                           (int))
                                     digit (if (= char "y")
                                             (-> r
                                                 (bit-and 0x3)
                                                 (bit-or 0x8))
                                             r)]
                                 (reset! now (.floor js/Math (/ @now 16)))
                                 (.toString digit 16))))))