pre-refactor-sample.js

// searches MongoDb for all users with a rank limit 10000
User.aggregate([
  {
    $project: {
      _id: "$_id",
      rank: "$rank"
    }
  },
  {
    $match: {
      rank: { $ne: null }
    }
  },
  { $limit: 10000 }
]).then(items => {
  items.forEach(function(i) {
    // Loops through each user to unset the rank
    User.findOneAndUpdate(
      { _id: i._id },
      { $unset: { rank: 1 } },
      { new: true }
    );
  });
});