Can javascript be used to get data from a remote server and populate a dropdown list?

New user alert:

I'm able to authenticate users via both SSO and by associating the user with a panel.

The panel entries contain embedded data fields that tell me various things, like the user's unit_ID (which department or office they're associated with).

Each unit has anywhere from 1 to 15 account numbers (nearly 400 numbers total).

I'd like to present users with a dropdown list of only the account numbers associated with their unit.

Because there are nearly 190 units, and because new account numbers are added periodically, I'd like to avoid using display logic if at all possible.

I know (or at least, I think) that javascript can be made to get data from a remote server if the data is formatted properly (I can put my data in JSON), and could filter the responses (match on unit_ID) and populate my dropdown list.

But that's all I know.

I have to be able to connect to a remote server, identify a file, filter by unit_ID, return the account numbers, and populate a dropdown list.

I'm not asking anyone to write the code for me, but maybe just point me in the right direction.

Any help would be greatly appreciated.