gistfile1.clj

(def path-cache (atom {}))

(defn load-cached [path]
  (if-let [ret (get @path-cache path)]
    ret
    (let [ret (cell nil)]
      (swap! path-cache assoc path ret)
      (XhrIo/send path 
                  (fn [e]
                    (case (.. e -target getStatus)
                      200 (reset! ret (.. e -target getResponseText))
                      (log "ERROR" "Request to" path e)))
                  "GET")
      ret)))

;; in this case, html-to-dom is passed a cell object

(def overlay 
  (cell (when-let [html (load-cached "/_static/html/backend-overlay.html")]
          (let [dom (domina/html-to-dom html)]
            (at js/document
                ["body"] (append dom))
            dom))))

;; in this case, html-to-dom is passed a nil from the first transition

(def overlay 
  (let [html (load-cached "/_static/html/backend-overlay.html")]
    (cell (when html
            (let [dom (domina/html-to-dom html)]
              (at js/document
                  ["body"] (append dom))
              dom)))))