Routes for a user controller in a Node.js application

Question

I have a very simple Node application that routes requests to /users to the following file:

users.js

var express = require('express');
var router = express.Router();
var User = require('models/user');
var sequelizeSuccessHandler = require('lib/sequelizeSuccessHandler');
var sequelizeErrorHandler = require('lib/sequelizeErrorHandler');
router.get('/', function(request, response) {
 User.findAll()
 .then(sequelizeSuccessHandler(response))
 .catch(sequelizeErrorHandler(response));
});
router.post('/', function(request, response) {
 User.create(User.params(request.body))
 .then(sequelizeSuccessHandler(response))
 .catch(sequelizeErrorHandler(response));
});
router.get('/:id', function(request, response) {
 User.findOne({where: {id: request.params.id}})
 .then(sequelizeSuccessHandler(response))
 .catch(sequelizeErrorHandler(response));
});
router.patch('/:id', function(request, response) {
 User.findOne({where: {id: request.params.id}})
 .then(function(user) {
 return user.update(User.params(request.body));
 })
 .then(sequelizeSuccessHandler(response))
 .catch(sequelizeErrorHandler(response));
});
router.delete('/:id', function(request, response) {
 User.findOne({where: {id: request.params.id}})
 .then(function(user) {
 return user.destroy();
 })
 .then(sequelizeSuccessHandler(response))
 .catch(sequelizeErrorHandler(response));
});
module.exports = router;

lib/sequelizeSuccessHandler.js

var Sequelize = require('sequelize');
function successHandler(response) {
 return function(object) {
 response.send(JSON.stringify(object));
 };
}
module.exports = successHandler;

lib/sequelizeErrorHandler.js

var Sequelize = require('sequelize');
function errorHandler(response) {
 return function(error) {
 if (error.constructor == Sequelize.ValidationError) {
 response.status(400).send();
 } else {
 response.status(500).send();
 }
 };
}
module.exports = errorHandler;

Looking at users.js, you can see that I tried to DRY things up by creating sequelizeSuccessHandler and sequelizeErrorHandler (I hate those names), but there's still a lot of repetition. I feel like there is a better way to do this.

How can I clean this up?

• Aaron Goldsmith: the database queries should be done in a separate controller

Answer 1

Looking at users.js, you can see that I tried to DRY things up by creating sequelizeSuccessHandler and sequelizeErrorHandler (I hate those names), but there's still a lot of repetition.

I suppose you're talking about these repeated lines in the route handlers:

 .then(sequelizeSuccessHandler(response))
 .catch(sequelizeErrorHandler(response));

I don't really know Node, but it seems to me that you could add another helper function:

function handle(query, response) {
 query
 .then(sequelizeSuccessHandler(response))
 .catch(sequelizeErrorHandler(response));
});
router.get('/', function(request, response) {
 handle(User.findAll(), response);
});
router.post('/', function(request, response) {
 handle(User.create(User.params(request.body)), response);
});

(The names "handle", and "query" might not be the best.)