On the surface, this question seems easy (and admittedly I am new to javascript so it may be), but here are the details:
The work I do is in Drupal, therefore I work predominately with CSS and Drupal's interface. However, for the current function I am doing, I need to use Javascript to add an overlay onto an existing Google map. I have already written the javascript, and the map is working, but the location of my javascript is inside the javascript of the module I am using to make the map. If I keep it there, then once the module updates, my work will be overridden by the new javascript. Therefore, what I need to do is add my functionality inside a new javascript file saved elsewhere that can effect the javascript inside the map module without having to write anything into the map module. I have seen plenty on this that requires a call to be placed in the original js file, but that won't work, as it will be overridden on the next update.