Collection.find() for array inside object
Something like this:
ChatGroups.find({whitelist: Meteor.user().username});This assumes that username is the property you want to match against. You don't need to do anything special to search within an array in this case - mongo will do the correct thing (compare username to each element of each whitelist and return those documents that match).
To search in MongoDB by array items - use $in operator:
ChatGroups.find({ whitelist: { $in: [Meteor.user()._id] }});Reference: Comparison Query Operators > $in