upload to memory

(defn file-input [{:keys [id doc multiple on-change hide-msg
                          preview directory on-raw-change] :as attrs}]
  [error {:errors (get (:bouncer.core/errors @doc) id) :hide-msg hide-msg}
   [:div.flex.flex1.flex-column {:style {:display "inline-block"}}
    (when (and preview (get @doc id))
      [preview (get @doc id)])
    [:div [:b (if multiple
                (apply str (interpose ", " (map :name (id @doc))))
                (:name (id @doc)))]]
    (let [attrs (merge
                 {:type "file"
                  :multiple (if multiple "multiple" "")
                  :on-change
                  (fn [e]
                    (let [target (.-target e)
                          files (.-files target)
                          a (atom [])]
                      (doseq [n (range (alength files))]
                        (let [file (aget files n)
                              reader (js/FileReader.) ]
                          (when on-raw-change
                            (on-raw-change file))
                          (aset reader "onerror" #(do
                                                    (println "ON ERROR")
                                                    (swap! a conj nil)))
                          (aset reader "onabort" #(do
                                                    (println "ON ABORT")
                                                    (swap! a conj nil)))
                          (aset reader "onloadend"
                                #(let [b64 (.-result (.-target %))
                                       b64 (.substring b64 (inc (.indexOf b64 ",")))]
                                   (swap! a conj {:file/name (.-name file) :file/data b64
                                                  :file/directory directory})
                                   (when (= (count @a) (alength files))
                                     (set! (.-value target) nil)
                                     (swap! doc assoc id
                                            (if multiple
                                              (vec (filter identity @a))
                                              (first @a)))
                                     (when on-change
                                       (on-change (id @doc))))))
                          (.readAsDataURL reader file)))))}
                 (dissoc attrs :on-change :multiple :id :doc :preview
                         :hide-msg :on-raw-change :directory))]
      [:input attrs])]])