Simple ExpressJS Hello World application

• Following tutorial on TutorialsPoint (lots of ads!)
• Express is a very widely used backend JS framework
• Frontend frameworks like Angular and React run in the browser, but Express runs on the server, using Node.JS
• We will do the first 4 sections in the tutorial, through the section “Hello World”
• Follow on down…

Prerequisites

• Install Node.JS that will also install the Node Package Manager (npm)
• Test in command prompt or terminal with:

  node --version
  npm --version
  

  which should give you the installed versions.

Create a project folder

• Run the commands:

  mkdir hello-world
  cd hello-world
  pwd
  

• Last command should show that you are inside the new project folder

Initialize your Node.JS project

• Create a package.json file with the following command:

  npm init -y
  

  (if you want control over what goes in it, omit the -y)
• Start installing Node packages for our project:

  npm install --save express
  

  which will download packages under the node_modules folder
  (the --save option will make an entry inside the package.json file)
• Install a global program to run your project:

  npm install -g nodemon
  

  which will install the nodemon utility system-wide
  (if you are on Mac or Linux, you would need to run this with sudo powers)

Your Hello World program

• Paste this into a new file named index.js (use any text editor):

  var express = require('express');
  var app = express();
  
  app.get('/', function(req, res){
      res.send("Hello world!");
  });
  
  app.listen(3000);
  

  It will create a route to the root ('/') of your website and print.
• Run it with the command:

  nodemod index.js
  

  which should display some information and wait until canceled.

Viewing your Express program

• Open your browser to http://localhost:3000
• It should display:

  Hello World
  

• If this basic Express program works, you can continue to the right to build an API

A RESTful API in Express.JS

• Following up on the Hello World application
• Create an api.js file with the contents:

  var express = require('express');
  var bodyParser = require('body-parser');
  var cookieParser = require('cookie-parser');
  var multer = require('multer');
  var upload = multer();
  
  var app = express();
  
  app.use(cookieParser());
  app.use(bodyParser.json());
  app.use(bodyParser.urlencoded({ extended: true }));
  app.use(upload.array());
  
  //Require the Router we defined in movies.js
  var movies = require('./movies.js');
  
  //Use the Router on the sub route /movies
  app.use('/movies', movies);
  
  app.listen(3000);
  

What’s new?

• Multiple packages loaded at the top. Install them first:

  node install --save body-parser
  node install --save cookie-parser
  node install --save multer
  

• An external file movies.js is loaded, which we will create in the next step.
• With app.use() an ExpressJS Router is set up for the /movies sub-URLs

Make the router component

• Create a new file movies.js:

  var express = require('express');
  var router = express.Router();
  var movies = [
      {id: 101, name: "Fight Club", year: 1999, rating: 8.1},
      {id: 102, name: "Inception", year: 2010, rating: 8.7},
      {id: 103, name: "The Dark Knight", year: 2008, rating: 9},
      {id: 104, name: "12 Angry Men", year: 1957, rating: 8.9}
  ];
  
  //Routes will go here
  module.exports = router;
  
  router.get('/', function(req, res){
   res.json(movies);
  });
  

  which returns a JSON in response to the root URL /, which now points under /movies where the Router is attached in api.js.

Running it

• Run with:

  nodemon api.js
  

• Point browser to http://localhost:3000/movies, which should show:

  [{"id":101,"name":"Fight Club","year":1999,"rating":8.1},
   {"id":102,"name":"Inception","year":2010,"rating":8.7},
   {"id":103,"name":"The Dark Knight","year":2008,"rating":9},
   {"id":104,"name":"12 Angry Men","year":1957,"rating":8.9}]