MongoDB $addtoSet and $set in the same operation

Question

In my Meteor/javascript app, I am trying to update a specific MongoDB document via $addToSet on a certain part of that document followed by $set on a different part of that same document. There is no overlap between these two portions, so from what I read online it should be safe. But I can't seem to get the syntax correct. How can I carry out these two operations in one javascript command? The below works as two separate commands, and I assume it would be faster if they could be combined into just one write to Mongo.

Collection.update(
  {_id: documentId},
  {$addToSet:
    {data:
      {$each: newData}
    }
  }
);
Collection.update(
  {_id: documentId},
  {$set:
    {lastTxn: lastTxn,
     updatedAt: new Date()}
  }
);

Answer 1

As long as they are not on the same path ( which is the one thing you cannot do ) then it is perfectly fine. The $set and $addToSet operations are just top level "keys" of the "update document":

 Collection.update(
  { "_id": documentId },
  {
    "$addToSet": { "data": { "$each": newData } },
    "$set": { 
       "lastTxn": lastTxn,
       "updatedAt": new Date()
    }
  }
);