Conversion functions between DataURL and Blob type

dataurl.cljs

;; Based on the implementations found here: https://gist.github.com/wuchengwei/b7e1820d39445f431aeaa9c786753d8e
(defn dataurl->blob
  [dataurl]
  (let [arr   (str/split dataurl #",")
        mime  (second (re-find #":(.*?);" (first arr)))
        bstr  (js/atob (second arr))
        n     (count bstr)
        u8arr (-> (map (fn [i] (.charCodeAt bstr i)) (range n))
                  (into-array)
                  (js/Uint8Array.from))]
    (js/Blob. (js/Array. u8arr) (js-obj "type" mime))))

(defn blob->dataurl
  [blob callback]
  (let [a (js/FileReader.)]
    (set! (.-onload a)
          (fn [e] (callback (-> e .-target .-result))))
    (.readAsDataURL a blob)))