clojure reagent interval subscription

reagent_interval.cljs

(ns com.widdindustries.reagent-interval
  "functions to create reagent reactions (ie ratoms) whose value changes 
  as an argument function is called periodically"
  (:require [reagent.ratom :as ratom]
            [reagent.core :as r]))

(defn interval-async 
  "create ratom whose value will initially be initial-state, 
  and thereafter may change as f is called with the 'state' atom every delay-ms"
  [f delay-ms initial-state]
  (let [state (r/atom initial-state)
        _ (f state)
        interval (js/setInterval (fn [] (f state)) delay-ms)]
    (ratom/make-reaction 
      (fn [] @state)
      :on-dispose (fn [] (js/clearInterval interval)))))

(defn interval-pure 
  "create ratom whose value will be the result of calling f every delay-ms"
  [f delay-ms]
  (interval-async 
    (fn [state] 
      (reset! state (f)))
    delay-ms 
    (f)))