Function (not macro) to clone javascript arguments object to array in the most jit-friendly way possible.

arguments-to-array.cljs

(defn- arguments-to-array
  "This is the most jit-friendly way to turn arguments into an array.
  js-this is a uint32 start index.

  Call *exactly* like so: (.apply arguments-to-array start-index (js-arguments))
  Any other call pattern will prevent optimizations in calling function.

  Returns a real js array of its arguments starting from start-index.
@param {...*} var_args"
  [var_args]
  (let [len (alength (js-arguments))
        a #js []]
    (loop [i 0 j (js-this)]
      (if (< j len)
        (do
          (aset a i (aget (js-arguments) j))
          (recur (inc i) (inc j)))
        a))))