Fire javascript every x page load, for example, every 3rd page

Question

I'm sure this question has been answered, before, but my searches are coming up empty.

I have a simple jQuery function (that slides in a box after the page has been scrolled down). It works fine.

However, how do I set cookies, or other method, to make it execute on the first page load and, then, on every 3rd page load of the session, after that?

Answer 1

A little snippet like this should work for you.

(function () {
  // Get the countdown from localStorage
  var countdown = Number(window.localStorage.getItem('countdown'));
  
  // If countdown isn’t set it or if it has
  // run a couple times it’ll be `0`
  // Either way—we reset countdown and run the function
  if (!countdown) {
    countdown = 3;
    // Run the function
  }

  // Update the countdown
  window.localStorage.setItem('countdown', countdown - 1);
})();