Generate keys for children in reagent component automatically

example.cljs

(defmacro defcomponent [name attrs & body]
  (let [i (.indexOf attrs '&)]
    (if (> i -1)
      (let [sym (get attrs (inc i))]
        `(defn ~name ~attrs
           ~@(postwalk-replace {sym `(with-idx ~sym)} body)))
      `(defn ~name ~attrs
         ~@body))))