hi i had an issue with classes can only be appended, (with a country flag icon).. how about:

(defn denormalize-class
  "Class denormalization for attribute providers."
  [kvs]
  (if (map? kvs)
    (s/join " " (keep (fn [[k v]] (when v (name k))) kvs))
    kvs))

(defmethod do! :class!
  [elem _ kvs]
  (let [elem  (js/jQuery elem)
        clstr (denormalize-class kvs)]
    (.addClass (.removeClass elem) clstr)))

interesting

you need to remove allthe classes then add them back?