//Router file. After doing all your imports at beginning of file
const router = express.Router();
app.use('/pathforpostrequests', router);

router.patch('/:name', controller.updatePerson, (req, res, next) => {
  res.status(200).json(res.locals.person);
});

// Controller file. After doing all your imports at beginning of file. Person is an example mongo schema you will need to setup in a schema file.
const controller = {
  updatePerson (req, res, next) {
    Person.findOne({ firstName: req.params.name }).exec()
    .then((result) => {
      result.firstName = req.body.firstName;
      result.save();
      res.locals.person = result;
      next();
    })
  },
}