MongoDB/Mongoose - Adding an object to an array of objects only if a certain field is unique
If you look into the documentation on your method you will see that the parameters passed are not in the proper order.
findByIdAndUpdate(id, update, options, callback)I would use update instead and have your id and portal.events.eventId": { $ne: req.body.eventId } part of the initial filter followed by $addToSet: { "portal.events": req.body }
Something among these lines:
UserModel.update( { "_id": mongoose.Types.ObjectId(userId), "portal.events.eventId": { $ne: req.body.eventId } }, { $addToSet: { "portal.events": req.body } }, { new: true });
You need to include your eventId check into condition part of your query. Because you're usig findByIdAndUpdate you can only pass single value matched against _id as a condition. Therefore you have to use findOneAndUpdate to specify custom filtering condition, try:
UserModel.findOneAndUpdate( { _id: userId, "portal.events.eventId": { $ne: req.body.eventId } }, { $addToSet: { "portal.events": req.body } }, { new: true });