How to reuse database controllers - node.js

Question

I'm trying to reuse my controllers which handle database operations. I'm bit struggling with structuring my application. Here's what I have:
server.js
var apiController = require('./controllers/api');
router.get('/cars', function (req, res) {
// get all cars from DB and render view
apiController.getCars().then(function (cars) {
res.render('index', {cars: cars});
});
});
router.get('/api/cars', function (req, res) {
// get all cars from DB and return JSON
apiController.getCars().then(function (cars) {
res.json(cars);
});
});
controllers/api.js
module.exports = {
getCars: function () {
db.collection('cars').find().toArray( function (err, cars) {
if (err) throw err;
return cars;
});
},
// tried also something like this but this doesn't really work
// for my use case because I don't want to attach any particular
// res to the function
getCars: function (req, res, next) {
db.collection('cars').find().toArray( function (err, cars) {
if (err) throw err;
res.json(cars);
});
},
};

Answer 1

Your current problem is that you expect promises as return in server.js while you use callbacks in the controller. I suggest you change your function getCars to return a Promise. Don't know what ODM/ORM you're using but it might look like something like this:
getCars: function () {
return db.collection('cars').find();
},

Answer 2

server.js
var apiController = require('./controllers/api');
router.get('/cars', function (req, res) {
apiController.get('cars').then(function (cars) {
res.render('index', {cars: cars});
});
});
router.get('/api/cars', function (req, res) {
apiController.get('cars').then(function (cars) {
res.json(cars);
});
});
controllers/api.js
var Promise = require('bluebird');
module.exports = {
get: function (modelName) {
return new Promise(function(resolve,reject){
return db.collection(modelName).find().toArray(function(err, models){
if (err) {
return reject(err);
}
else {
return resolve(models);
}
});
});
}
};

Answer 3

server.js
var apiController = require('./controllers/api');
router.get('/cars', apiController.getCars);
controllers/api.js
function getCarsAsync(req, res, next){
db.collection('cars').find().then(function(carsData){
if(carsData){
return res.send(carsData);
}
else{
return res.status(401).send('User is not authorized');
}
}).catch(function(err){
return next(err);
});
}
module.exports = {
getCars: getCarsAsync
};