The Complete Node.js Course: Building RESTful APIs Using Express

Introduction

This chapter will introduce the express npm module for building scalable web applications.

Recall that in the HTTP module introduction, we had this code to implement a simple web app that implemented responses for / and /friends:

const http = require('http');
const server = http.createServer((req, res) => {
  if (req.url === '/') {
    res.write('Hello World');
    res.end();
  }

  if (req.url === '/friends') {
    res.write(JSON.stringify(
      ['James', 'Frank', 'Ittai', 'Stas']
    ))
  }
});

server.on('connection', (socket) => {
  console.log('New connection...');
});

server.listen(3000);

console.log('Listening on port 3000...');

As this web app is extended, a new if block would need to be added for each route. This is not scalable or maintainable.

The express framework is a fast, minimalist web framework for node that helps build maintainable web applications.

RESTful Service

REST is an implementation of the client server architecture.

REST is short for "REpresentational State Transfer". It is a convention for building HTTP services. It defines a protocol to Create, Read, Update, and Delete data. These operations are know as CRUD operations.

In REST, you expose data objects as URL end points. For example, you might use the following URL might be the end point to access customers:

http://example.com/api/customers

All operations on customer objects are implemented as an HTTP request to this end point. The type of HTTP request defines the kind of operation to perform.

HTTP Request Type	Operation
GET	Reads objects
POST	Creates new objects
PUT	Updates objects
DELETE	Deletes Objects

A RESTful application is a web application that follows these conventions:

• It exposes resources (aka objects) using a simple meaningful address (like /api/customers for customers)
• It supports various operations on those resources such as creating or updating those resources
• It implements calling those operations via a set of standard HTTP methods
• It represents data received or data sent as JSON

Here is how a RESTful application might expose customer resources:

Operation	HTTP Method & URL	Request Body	Response Body
Get customers	GET /api/customers	N/A	List of customers
Get a customer	GET /api/customers/{id}	N/A	A single customer
Update a customer	PUT /api/customers/{id}	Customer properties to update	The updated customer
Delete a customer	DELETE /api/customers/{id}	N/A	The deleted customer
Create a customer	POST /api/customers	A customer	The new customer with its id

Introducing Express

Express is a framework gives our web application structure so that we can easily add new routes while keeping our application maintainable.

Create a project and install express:

1. Create a project directory

   Projects $ mkdir express-demo
   Projects $ cd express-demo
   express-demo $
   

2. Run npm init

   express-demo $ npm init --yes
   Wrote to /Users/couballj/SynologyDrive/Documents/Projects/express-demo/package.json:
   
   {
     "name": "express-demo",
     "version": "1.0.0",
     "description": "",
     "main": "index.js",
     "scripts": {
       "test": "echo \"Error: no test specified\" && exit 1"
     },
     "keywords": [],
     "author": "",
     "license": "ISC"
   }
   
   
   express-demo $
   

3. Install express

   express-demo $ npm install express
   
   added 57 packages, and audited 58 packages in 2s
   
   7 packages are looking for funding
     run `npm fund` for details
   
   found 0 vulnerabilities
   express-demo $
   

Building Your First Web Server

Add an index.js file as follows:

const express = require('express');
const app = express();

 app.get('/', (req, res) => {


 });

Nodemon

Environment Variables

Route Parameters

Handling HTTP GET Requests

Handling HTTP POST Requests

Calling Endpoints Using Postman

Input Validation

Handling HTTP PUT Requests

Handling HTTP DELETE Requests

Build the Genres API App

Recap