¿Alguna forma en JavaScript del cliente para saber si el usuario actual es miembro de un grupo privado?

[Falco]

For the current user, this will be done soon:

Plugin Development: List a user’s groups without making a request

@maja, can you add that to your list? We should always serialize all the group names of the current user (not only the primary group).

This will be enough for you to

@merefield

hide a javascript built advertising panel from site donators

and is the exact use case I had in mind.