Nodejs and mongoDB objectId failed for value

hello everyone ! i got this error and i can’t solve it so please any help would be greatly appreciated!

Error: CastError: Cast to ObjectId failed for value "{ id: 'wishlist' }" (type Object) at path "_id" for model "Product"
here is the code:
const addtowishlist = asyncHandler(async(req,res)=>{
            const {_id} = req.user;
            const{prodId} = req.body;
            try {
                const user = await User.findById(_id);
                const alreadyadded = user.wishlist.find((id)=>id.toString()=== prodId);
                if(alreadyadded){
                    let user = await User.findByIdAndUpdate(
                        _id,
                        {
                        $pull: {wishlist: prodId},
                        },
                        {
                            new: true,
                        }
                    );
                    res.json(user);
                }
                else{
                    let user = await User.findByIdAndUpdate(
                        _id,
                        {
                        $push: {wishlist: prodId},
                        },
                        {
                            new: true,
                        }
                    );
                    res.json(user);
                    

                }
                
            } catch (error) {
                throw new Error(error)
            }
        })

pleaaaaaaaaase any help !!!

try to provide more context and explain what debugging you already did, it may be that with missing context it’s not easy to help