counter.clj

(:require [cljs.core.async :as a]
          [dommy.core :as d]
          [clidget.widget :refer [defwidget] :include-macros true])
(:require-macros [dommy.macros :refer [node]]
                 [cljs.core.async.macros :refer [go-loop]]))

(defwidget counter-widget [{:keys [counter]} events-ch]
  (node
   [:div
    [:h2 "counter is now: " counter]
    [:p
     (doto (node [:button "Increment counter"])
       (d/listen! :click #(a/put! events-ch :inc-counter)))]]))

events.clj

(defn watch-events! [events-ch !counter]
  (go-loop []
    (when-let [event (a/<! events-ch)]
      (when (= :inc-counter event)
        (swap! !counter inc))
      (recur))))

include.clj

(set! (.-onload js/window)
      (fn []
        (let [!counter (atom 0)
              events-ch (doto (a/chan)
                          ;; 'watch-events!' implemented below
                          (watch-events! !counter))]

          (d/replace-contents! (.-body js/document)
                                    (counter-widget {:!counter !counter} events-ch)]))))