History

This is some code taken from the secretary history example:

;; Quick and dirty history configuration.
(let [h (History.)]
  (goog.events/listen h EventType.NAVIGATE #(secretary/dispatch! (.-token %)))
  (doto h
    (.setEnabled true)))

The first event from goog.History.Event has a token set to "". For many applications, it is useful to handle the case differently. You might try this:

(let [h (History.)
      f (fn [he] ;; goog.History.Event
          (.log js/console "navigate %o" (clj->js he))
          (let [token (.-token he)]
            (if (seq token) ;; preferred over (not (empty? token))
              (secretary/dispatch! token)))))]
  (events/listen h EventType/NAVIGATE f)
  (doto h (.setEnabled true)))

Another way (perhaps better) is to test isNavigation. From history.Event:

isNavigation : boolean True if the event was triggered by a browser action, such as forward or back, clicking on a link, editing the URL, or calling window.history.(go|back|forward). False if the token has been changed by a setToken or replaceToken call.