messing with transit to avoid the clj->js tax

transit.cljs

    (require '[cognitect.transit :as t])
    
    (def jt js/transit)
    
    (def r (t/reader :json))
    (def w (t/writer :json))
    
    (def jr (jt.reader "json"))
    
    
    (def the-obj (clj->js {"a" [1 2 3] "b" [4 5 6] "c" {"d" {"e" [7 8 9]}}}))
    (def the-json (js/JSON.stringify the-obj))
    
    (defn map->obj [m]
      (let [res #js{}]
        (.forEach m (fn [v k]
                      (if (transit.isMap v)
                        (aset res k (map->obj v))
                        (aset res k v))))
        res))
    
    (defn demo-transit [json-txt]
      (let [m            (t/read r json-txt)
            {a "a" b "b"} m
            result (assoc m "z" (+ (a 0) (b 0)))]
        (map->obj (.read jr (t/write w result)))))
    
    (defn demo-cljs [json-txt]
      (let [m            (js->clj (js/JSON.parse json-txt))
            {a "a" b "b"} m
            result (assoc m "z" (+ (a 0) (b 0)))]
        (clj->js result)))


#_
(defmacro jslet [bindings & body]
  (let [new-binds (->> (for [[l r] (partition 2 bindings)]
                         (if (and (map? l) (l :fields))
                           (let [flds   (l :fields)
                                 fbinds (for [f flds]
                                          `[~f (aget ~r ~(name f))])]
                             (apply concat fbinds))
                           [l r]))
                       (apply concat))]
    `(let [~@new-binds] ~@body)))



     (defn demo-js [json-txt]
       (let [m            (js/JSON.parse json-txt)
             a (aget m "a")
             b (aget m "b")]
         (aset m "z" (+ (nth a 0) (nth b 0)))
         m))

    ;; cljs.user> (demo-transit the-json)
    ;; #js{:a #js[1 2 3], :b #js[4 5 6], :c #js{:d #js{:e #js[7 8 9]}}, :z 5}
    ;; cljs.user> (demo-cljs the-json)
    ;; #js{:a #js[1 2 3], :b #js[4 5 6], :c #js{:d #js{:e #js[7 8 9]}}, :z 5}

    ;;cljs.user> (demo-js the-json)
    ;;#js{:a #js[1 2 3], :b #js[4 5 6], :c #js{:d #js{:e #js[7 8 9]}}, :z 5}

    ;; cljs.user> (time (dotimes [i 10000] (demo-cljs the-json)))
    ;; "Elapsed time: 297.000000 msecs"
    
    ;; cljs.user> (time (dotimes [i 10000] (demo-transit the-json)))
    ;; "Elapsed time: 136.000000 msecs"
    ;;nil

    ;;cljs.user> (time (dotimes [i 10000] (demo-js the-json)))
    ;;"Elapsed time: 13.000000 msecs"