Facebook major API change sucks but we have to deal with it. The page endpoint got a new "context" field which returns the number of friends who like this page, and the identity of the friends who also installed my app.
For example:
/v2.0/579302565453830?pretty=1&fields=context.fields(mutual_friends.limit(1000))
This is possible according to the new documentation: https://developers.facebook.com/docs/facebook-login/social-context/v2.0
I can also get the members of a group, for instance:
/v2.0/573611446041812/members
How can I mix it and get only the members (or at least number of members) that are my friends? /me/friends returns only friends that use my app so this is not an option.
As /v2.0/me/friends returns only app-using friends, its only possible to surface to a user the subset of a group's members, who are friends of the user, where those friends also use the app.
There is currently no friends_who_are_members (or similar) context edge on the Group node.