Liam Goodacre

Tail-call optimised recursive looping in JavaScript

Even though I should be carrying on building my game that is in on Wednesday, I had a spark of procrastination and built a JavaScript function to allow optimised tail-call recursion in JavaScript.

I based it on the Clojure Loop construct:

;;; Calculate Factorial of 5
(loop [n 5 acc 1]
  (if (pos? n)
      (recur (dec n) (* acc n))
      acc))

The following is the equivalent loop call in JavaScript, using my new loop and recur functions:

loop({n: 5, acc: 1}, function (recur, data) {
  if (data.n > 0) {
    return recur({n: data.n - 1, acc: data.acc * data.n});
  }
  return data.acc;
});

Although it is a little nasty to have to use the data object, it does in fact work pretty well.

The implementation code is published on my GitHub at: JSLoop

Now back to my game development.