Comment by diggan

Did someone say concise? Here is a ClojureScript + Reagent example for whoever is interested in that:

  (defn Counter [{:keys [label counterType onClick]
                  :or {onClick (fn [])}}]
    (let [count (r/atom 0)]
      [:button
        {:onClick #(do (swap! count (condp = counterType
                                      :increment inc
                                      :decrement dec))
                       (onClick))}
        (str label ": " @count)])))