JAVASCRIPT

Mongoose DELETE

// Delete a user by username
app.delete('/users/:Username', (req, res) => {
  Users.findOneAndRemove({ Username: req.params.Username })
    .then((user) => {
      if (!user) {
        res.status(400).send(req.params.Username + ' was not found');
      } else {
        res.status(200).send(req.params.Username + ' was deleted.');
      }
    })
    .catch((err) => {
      console.error(err);
      res.status(500).send('Error: ' + err);
    });
});

MONGOOSE delete

Modelname.findOneAndDelete({ id: id })

delete document mongoose

Tank.deleteOne({ size: 'large' }, function (err) {
  if (err) return handleError(err);
  // deleted at most one tank document
});

how to delete popultate subdocument mongoose

Surf
    .find({user_id: {$in: userIds}})
    .populate('user_id', 'name boards') // added boards
    .populate('friends', 'name')
    // .populate('board_id', 'name size') // can't do this as discussed
    .exec(function (err, surfs) {
      if (err) {
        return handleError(res, err);
      }

      surfs.forEach(function (surf) {
        surf.set('boardInfo', surf.user_id.boards.id(surf.board_id), {strict: false});
      });
      // TODO: now remove the surf.user_id.boards.
      return res.json(200, surfs);
    });

mongoose undo delete

No,
You cannot undo a delete operation.
Once deleted the data cannot be retrieved UNLESS a dump of the collections is created
before deleting it.

mongoose remove

const res = await Character.remove({ name: 'Eddard Stark' });
res.deletedCount; // Number of documents removed