User controller

The server/controllers/user.controller.js file will contain the controller methods used in the preceding user route declarations as callbacks when a route request is received by the server.

The user.controller.js file will have the following structure:

import User from '../models/user.model'
import _ from 'lodash'
import errorHandler from './error.controller'

const create = (req, res, next) => { … }
const list = (req, res) => { … }
const userByID = (req, res, next, id) => { … }
const read = (req, res) => { … }
const update = (req, res, next) => { … }
const remove = (req, res, next) => { … }

export default { create, userByID, read, list, remove, update }

The controller will make use of the errorHandler helper to respond to the route requests with meaningful messages when a Mongoose error occurs. It will also use a module called lodash when updating an existing user with changed values.

lodash is a JavaScript library which provides utility functions for common programming tasks including manipulation of arrays and objects. To install lodash, run npm install lodash --save from command line. 

Each of the controller functions defined previously are related to a route request, and will be elaborated on in relation to each API use case.