Using the MongoDB projection parser (mongoose, NodeJS)

Question

MongoDB

Good evening.
There is a certain function
findUsers(ids, projection, callback){...}
The function accepts a list of user IDs, fields to be selected and, accordingly, a callback.
The function first searches for the specified users in Redis (users are stored serialized in string keys). If there are none, then it gets the missing ones from the mongo, after which it caches them, so that with the next same request, respectively, all these users are already taken from the cache. When contacting the mongo for the missing users, we take the document in full (do not use the projection passed in the second argument), because we will need to put the user in the cache.
Thus, the function glues data from radish and mongi (+ caches). The catch is that before passing the result to the callback, I need to filter them and return only those fields that were requested (via projection, the second argument to the function).
Is it possible to somehow use the native parser that is used inside the .find, findOne methods? Those. feed it my glued result object and projection and have it filter it all out. I need projections like {wishes.$.title: 1} to be handled correctly.
Can you do without your bikes?

Answer 1

As far as I understand, the MongoDB driver only builds queries. All logic lies on the shoulders of MongoDB itself. Instead of blocking the bike, use pick()Underscora/Lo-Dash.