ClojureScript stopwatch

stopwatch.cljs

(ns stopwatch)

(defn seconds-to-time
  [secs]
  (let [d (js/Date. (* secs 1000))]
    {:hours   (.getUTCHours d)
     :minutes (.getUTCMinutes d)
     :seconds (.getUTCSeconds d)}))

(defn display-time
  "Pretty-prints minutes:seconds, given time map of the form {:hours x :seconds y}."
  [tm]
  (let [pad (fn [n]
              (if (< n 10)
                (str "0" n)
                n))
        mm (pad (:minutes tm))
        ss (pad (:seconds tm))]
    ;;    (str mm ":" ss) <-- if you were to actually use this to update the DOM
    (.log js/console (str mm ":" ss))))

(def clock (atom 0))
(def start-time (atom 0))
(def time-fn (atom inc)) ;; included so we can swap it out for countdowns

(defn keep-time [func]
  (display-time (seconds-to-time @clock))
  (swap! clock func))

(defonce interval (atom 0))

(defn pause []
  (js/clearInterval @interval))

(defn start []
  (reset! interval (js/setInterval #(keep-time @time-fn) 1000)))

(defn reset []
  (js/clearInterval @interval)
  (reset! clock @start-time))