I'm a little confused about what you're trying to achieve with that query.

The first object passed to .find specifies some search criteria, so you're fetching all users except the one with _id === userid.

The second object specifies which fields to include in the output, equivalent to a $project stage. You're creating a new field "friendsList", and pass in an expression {$ne:userid}.

First thing is, you'd have to pass an array to $ne, specifying which values to compare, something like: { $ne: [ '$friendsList._id', userid ] }

However, I'm not sure if that'll do what you expect, because that will return documents with a "friendsList" field and a Boolean as value.

Generally, I don't think it's possible to filter with $project. Assuming that you do want to filter, put it into the first object. Maybe you're looking for something like this? User.find( { _id: { $ne: userid }, friendsList: { $ne: userid } } )

That would return a list of users where

• _id !== userid (-> all users except one)
• userid is not present in the friendsList

So basically a list of people who aren't friends with Mr. Userid.

Hope that answered your question.