How to aggregate document.ready actions?
In Drupal, $(document).ready() is not used. The Drupal API uses Drupal.behaviors.

You didn't mention your version of Drupal. But you can read about the Drupal 7 JavaScript API here: https://www.drupal.org/node/756722

Here is Drupal 8: https://www.drupal.org/node/2269515

And here is a pretty comprehensive breakdown/tutorial I wrote on using the D7 API: http://www.jaypan.com/tutorial/high-performance-javascript-using-drupal-7s-javascript-api