Request Animation Frame Channel

raf.cljs

(defn animation-frame
  "Return a channel which will close on the nth next animation frame."
  ([] (animation-frame 1))
  ([n] (animation-frame n (async/chan 1)))
  ([n out]
     (js/window.requestAnimationFrame
      (fn [timestamp]
        (if (= n 1)
          (do
            (async/put! out timestamp)
            (async/close! out))
          (animation-frame (dec n) out))))
     out))