db.cljs

(defn update-user
  ([^js db user]
   (update-user db user nil))

  ([^js db user prev-username]
   (let [batch (.batch db)]
     (update-user db batch user prev-username)
     (.commit batch)))

  ([^js db batch-or-transaction user prev-username]
   (let [user-id (:id user)
         username (:username user)]

     (.update batch-or-transaction
              (user-profile-doc-ref db user-id)
              (clj->js (dissoc user :id)))

     (when (and prev-username
                (not= (user-profile/normalize-username prev-username)
                      (user-profile/normalize-username username)))
       (.delete batch-or-transaction
                (username-doc-ref db (user-profile/normalize-username prev-username))))

     (when (not= (user-profile/normalize-username prev-username)
                 (user-profile/normalize-username username))
       (.set batch
             (username-doc-ref db (user-profile/normalize-username username))
             (clj->js {:uid user-id}))))))