Express Setup

Express Setup 2min read

Post 02 in a series of posts about writing an Express REST API using Sequelize object rational mapping for SQL databases.

In this post we will steps through setting up the express server within the project

Install NPM Dependencies

Lets start by install the express module and dotenv.

Dotnev is helpful because we can set our environmental variables to use during development in a .env file and add it to the .gitignore to avoid sharing secret information with the internet.

npm install --save express dotenv 
Terminal command to install Express

Create Folder / File Structure

Next lets create a view folders and files to separate responsibilities and structure the express server app.

mkdir src
mkdir src/config
touch src/config/server.config.js
touch src/config/index.js
touch src/app.js
touch .env
Terminal commands to create Express folder structure

Server Config

We use this file to configure the server before importing it into our app.js file to start listening for http requests

// ./src/config/server.config.js

import express from 'express';

// Set variables based on NODE_ENV
let defaultPort;
switch (process.env.NODE_ENV) {
  case 'production':
    defaultPort = 8080;
  case 'development':
    defaultPort = 3000;
  case 'test':
    defaultPort = 3333;
    defaultPort = 3000;

 * --------------
 * An instance of the Express sever
 * @name server
 * @returns {object} Express server instance
const server = express();

// Set the server port
server.set('port', process.env.HTTP_PORT || defaultPort);

export default server;

Config Index

To keep our code neat and readable, we will create a config index file that will export each of the config files. Making for neat import statement when requiring.

// ./src/config/index.js

export { default as server } from './server.config'; // I need to be last because I am the server and require everything

Express Server App

Import our server config and start listening for http requests

import { server } from './config';

/** @type {Number} The http port number to listen for http request on  */
const port = server.get('port');

// Start listening for http requests
server.listen(port, () => {
  console.log(`SERVER: Running on port ${port}`);

 * --------------
 * Express server export for testing
 * @name server
 * @returns {object} Express server instance configuration
export default server;

Environmental File

Keep our secret information in the .env file and git ignore the file to avoid uploading it to the repository for the internet to find.

We require the dotenv file when starting nodemon in the package.json file below


NPM Run Scripts

Add a few npm run script to load and test the express server.

clear; will clear the terminal window before executing the npm script

nodemon we setup in post 01, and is a utility to automatic reload our node instance when a file change is detected

--require dotenv/config loads the .env file before executing the app entry point

--exec babel-node will transpile our ECMAScript project prior to executing

  "scripts": {
    "dev": "clear; nodemon --require dotenv/config --exec babel-node src/app.js",
    "start": "NODE_ENV=production babel-node src/app.js",
    "test": "clear; NODE_ENV=test mocha"

Testing with Mocha Chai

We are aiming to have a test driven development project, with maximum test coverage.

So we want to setup our test environment

npm install --save-dev mocha chai
Terminal commands to install development dependencies

Create Folder & File Structure

Lets setup the folder and file structure for our testing environment.

touch .mocharc.yml
mkdir test
mkdir test/unit
mkdir test/unit/config
touch test/unit/app.spec.js
touch test/unit/config/server.config.spec.js
Terminal commands to setup our testing environment
// ./test/unit/app.spec.js

import { assert } from 'chai';
import app from '../../src/app';

describe('Unit :: Express Server App', () => {
  it('expect the Express server app to be callable', (done) => {
    assert.equal(typeof app, 'function');
app.js testing specification
// ./test/unit/config/server.config.spec.js

import { assert, expect } from 'chai';
import { server } from '../../../src/config';

describe('Unit :: Config :: Server', () => {
  it('expect server config to default port to 3333 for testing', (done) => {
    const port = server.get('port');
server.config.js testing specification

Test everything is works

npm test
Terminal command to test our files
SERVER: Running on port 3333

  Unit :: Express Server App
    ✓ expect the Express server app to be callable

  Unit :: Config :: Server
    ✓ expect server config to default port to 3333 for testing

  2 passing (11ms)
Terminal out from test command

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