how can i check that which user belongs to which community group

I have created there group inside community(not role)..it is community group..i want to check if user belongs to it then i want to repalce custom conent inside content.

if(user belongs to abccommunitygroup)

{

  "he belongs to abc community group";

}

else

{

do something else;

}

Note:From Group i mean Community Group not role