// $out does NOT take effect here
db.collection('names')
  .aggregate([
    { $match: {} }, { $limit: 1 },
    { $out: 'newNames' }
  ], (err, cursor) => {
    callback();
  });



// $out DOES take effect here
db.collection('names')
  .aggregate([
    { $match: {} }, { $limit: 1 },
    { $out: 'newNames' }
  ], (err, cursor) => {
    cursor.toArray(function (err, documents) {
      console.log(documents);
      callback();
    });
  });