my attempt at an expressjs route

app.js

/* relevant section of my db module */

db.user = {};
db.user.available = function(email) {
	return knex('users')
		.where('email', email)
		.then(areNone);
};
db.user.add = function(data) {
	return knex('users')
		.insert({
			first_name : data.firstName,
			last_name : data.lastName,
			identity : data.identity,
			email : data.email,
			salt : data.salt,
			password : data.password
		}, 'user_id')
		.then(getFirst);
};
db.company.add = function(data) {
	return knex('companies')
		.insert({
			company_name : data.companyName,
			company_description : data.companyDescription,
			user_id : data.userId
		});
};
app.set('db', db);

/* route definition */

app.route('/register')
	.all(restrict)
	.get(function(req, res) {
		res.render('register');
	})
	.post(function(req, res) {
		trim(req.body);
		/* valid[model].validate returns either null (no error) or a string error message */
		var errMessage = valid.user.validate(req.body);
		if (errMessage) {
			req.session.error = errMessage;
			res.redirect('/register');
		} else {
			app.get('db').user.available(req.body.email).then(function(isAvailable) {
				if (isAvailable) {
					req.body.salt = bcrypt.genSaltSync();
					req.body.password = bcrypt.hashSync(req.body.password, req.body.salt);
					app.get('db').user.add(req.body).then(function(userId) {
						req.body.userId = userId;
						app.get('db').company.add(req.body).then(function() {
							req.session.success = "Account registration success";
							res.redirect('/register');
						});
					});
				} else {
					req.session.error = "Sorry, your email address has already been registered";
					res.redirect('/register');
				}
			});
		}
	});