Drupal alter some javascript of contrib module? I am working on a project that implements the Drupalchat module.
Everything works perfectly, but the client requests some custom changes.

They want people to be unable to have private conversations with eachother, but they do need to be able to see eachother!

They can only chat in the public chatroom, that Drupalchat provides by default.

A moderator user (drupal user role) however can chat privately with other users.

Is there a clean way to "hook" into the drupalchat.js file and alter the behaviour for this?

I have found the portion of code that needs to be altered, but of course I don't want to hack the contrib module.

I tried IRC about this, but nobody seemed to have a clue how to implement this.

Anyone done something like this in the past?

Thanks in advance!
I believe this has already been answered here: How to override jQuery from contrib module

To override the JavaScript file added to a page from a module, you need to implement hook_js_alter()....