Mongoose: remove() returns true for already deleted items

The problem with the above approach is that userNotFound will always be undefined since you haven't defined it in the callback arguments. Better to use the findOneAndRemove() function so that you can return the document removed if found:

var itemId = 123;Item.findOneAndRemove({ id: itemId })     .exec(function(err, item) {        if (err) {            return res.json({success: false, msg: 'Cannot remove item'});        }               if (!item) {            return res.status(404).json({success: false, msg: 'User not found'});        }          res.json({success: true, msg: 'User deleted.'});    });

Mongoose's Query#remove accepts a callback with 2 parameters:

1. error
2. writeOpResult

If you check the writeOpResult object, you should easily be able to tell whether deletion occurred or not.

It should contain a field called nRemoved. If it is 0 then no document was deleted, otherwise if it is a number then that many documents have been deleted. Similarly it has a field called nMatched which tells you how many documents matched your query.

So for your case it becomes like this:

var itemId = 123;Item.remove({id: itemId}, function(error, writeOpResult) {    if (error) {        return res.json({success: false, msg: 'Cannot remove item'});    }    if (writeOpResult.nMatched === 0) {        return res.status(404).json({success: false, msg: 'User not found'});    }    res.json({success: true, msg: 'User deleted.'});});