Arrays - JavaScript, how to make a double array?

Question

JavaScript

I have two variables:

var aid = 123
var bid = 321

One of them is the ID of a certain group, the second is a specific member of the entire group.
How can I make sure that in each group a participant with the same ID has different accounts, and there are many such "users"? (the server is also not alone.) Who did not understand: these are the profiles of the DS bot, where the value will be stored.