Creating a REST API with Node.js: 4 Easy Steps

The hype surrounding Application Programming Interfaces (APIs) is universal. It offers a software interface that facilitates the interaction between two applications, which is critical for scalability and reusability. It is now very common for proprietary web applications or services to have Public APIs. Other developers can leverage these to quickly combine features like Social Media Logins, Credit Card Debts, and Performance Tracking.

The standard they use for this is called Representational State Transfer (REST), and it works perfectly with the Node.js development techniques. Owing to this level of compatibility building a Node js REST API makes absolute sense.

Upon a complete walkthrough of this article, you will gain a holistic understanding of Node js and REST APIs. This article will also provide you with a detailed step-by-step guide on how to create API in Node js from scratch. Read along to learn more about Node js REST API!

Table of Contents

• Prerequisites
• What is REST API?
• What is Node.js?
• Steps to Build a Secure Node JS API
  • Step 1: Create the Required Directories
  • Step 2: Create your First App Express API
  • Step 3: Creating the User Module
  • Step 4: Creating the Auth Module
• Conclusion

Prerequisites

• Hands-on experience with JavaScript.
• Node js installed on the system.

What is REST API?

A RESTful API, also known as REST API, is based on Representational State Transfer (REST), which is an architectural style and communication approach commonly used in the development of Web Services.

In general, REST technology is preferred over other similar technologies. This is because REST consumes Less Bandwidth, making it more suitable for efficient Internet usage. RESTful APIs can also be designed using programming languages like JavaScript or Python.

While REST can be used over nearly any protocol, it is most commonly used for Web APIs over HTTP protocol. This means that developers do not need to install any additional libraries or software to take advantage of a REST API design.

REST has the ability to handle multiple types of Calls, Return Different Data Formats, and Even Change Structurally with the proper implementation of hypermedia as data is not tied to methods and resources. By leveraging the freedom and flexibility inherent in the REST API design, you can create an API that meets your needs while also meeting the needs of a wide range of customers.

What is Node.js?

Node.js is an Open-Source Server-Side Runtime Environment that is solely based on the V8 JavaScript Chrome Engine. It offers an Event-driven, Non-Blocking (Asynchronous) I/O and Cross-Platform runtime environment for developing highly scalable Server-Side JavaScript applications.

Node.js can be used to create a variety of applications, including Command-Line Applications, Web Applications, Real-time Chat Applications, REST API Servers, and so on. Its Event-Driven Runtime handles all types of HTTP requests and sleeps when not required. This allows developers to leverage JavaScript and write Server-Side scripts to generate Dynamic Web Content before it is delivered to the user’s web browser.

Later in this article, you will also learn about the process of building a secure Node js REST API.

Steps to Build a Secure Node JS REST API

Building a Node js REST API is a four-step process. Follow the steps given below to build a secure Node js REST API:

• Step 1: Create the Required Directories
• Step 2: Create your First App Express API
• Step 3: Creating the User Module
• Step 4: Creating the Auth Module

Step 1: Create the Required Directories

The first step involved in building a Node js REST API requires you to create directories that will contain the code for the Node js REST API.

• To begin with, open the Command Line Terminal on your system and navigate to the record where you usually create your projects and build a new directory which will consist of the Node js REST API’s code there using the following command:

 mkdir express-ads-api

• Now move to the directory you just created and practice npm install to frame a new project:

npm init -y

• If you open this directory in a text editor or an IDE, you’ll see that the npm command you used created a file called package.json. If you open this file, you’ll come across something like this:

• This data is currently quite insignificant and does not contain a lot of valuable information. Nevertheless, as you begin computing mandates for your project to create the Node js REST API, this file will grow in size. Following that, you will create a new directory called src within the design source by using the following command:

mkdir src

• The goal here is to include all your reference code that will be used to create the Node js REST API within this directory. So, after creating this directory for the Node js REST API, create a new file called index.js within it and add the following code to it:

    // ./src/index.js 
    console.log('Hello there!'); 

• After saving this file, run the following command to experiment with it:

node src

• Upon running this command, you will see a ‘Hello there!’ message prompted on your screen.

Step 2: Create Your First App Express API

Now, the project you just created simply logs a latent message. As this might not add much value to your project, you can start developing your Node js REST API. Follow the steps given below to do so:

• Open your command line and add the following code to it:

 npm install body-parser cors express helmet morgan

This command will create the following five dependencies in your design:

1. body-parser: This dependency will be used to convert the base of incoming applications into JavaScript objects.
2. cors: Cross-Origin Resource Sharing(CORS) is a dependency that is used to configure Express to combine headers specifying that your Rest API accepts requests from any source. 
3. express: This dependency denotes the Express library.
4. helmet: This module establishes different HTTP headers to safeguard Express APIs.
5. morgan: This package extends your Express Rest API’s logging capabilities.

• You need to mark two items in your project after initiating the previous command. The package.json file with all the libraries before it will include an original feature called dependencies.
• This is how NPM determines which dependencies are required by the project. Second, in the project root, you’ll find a new file named package-lock.json.
• It might take a few seconds based on your Internet connection for NPM to connect these dependencies. Once the dependencies are connected, you can initiate the index.js file and replace its code as follows to create the Node js REST API:

// ./src/index.js
// importing the dependencies
const express = require('express');
const bodyParser = require('body-parser');
const cors = require('cors');
const helmet = require('helmet');
const morgan = require('morgan');

// defining the Express app
const app = express();
// defining an array to work as the database (temporary solution)
const ads = [
  {title: 'Hello, world (again)!'}
];

// adding Helmet to enhance your Rest API's security
app.use(helmet());

// using bodyParser to parse JSON bodies into JS objects
app.use(bodyParser.json());

// enabling CORS for all requests
app.use(cors());

// adding morgan to log HTTP requests
app.use(morgan('combined'));

// defining an endpoint to return all ads
app.get('/', (req, res) => {
  res.send(ads);
});

// starting the server
app.listen(3001, () => {
  console.log('listening on port 3001');
});

This code represents two important things:

• An array called ads functions briefly as an In-Memory database.
• An endpoint that accepts HTTP GET requests and, when triggered, returns all of the items in the ads array.

Step 3: Creating the User Module

You can use Mongoose, an Object-Oriented Data Modelling(ODM) library to create the User Guide within the User Schema that will help you in creating a Node js REST API. Follow the steps given below to create the user module for your project:

• Create a new schema by using the commands given below:

/users/models/users.model.js:
const userSchema = new Schema({
	firstName: John,
	lastName: John,
	email: John,
	password: John,
	permissionLevel: Number
});

• Now, simply connect the schema to the User Module by using the following command.

const user model = mongoose.model('Users', userSchema);

• Once you have connected the schema to the User Module, you can leverage this model to perform all of the CRUD operations that are required within the Express endpoints.
• You can configure the “Create User” operation by finding the way in users/routes.config.js:

   app.post('/users', [
	UsersController.insert
           ]);

• This is enticed into the Express app via the main index.js file. As determined in /users/controllers/users.controller.js, the UsersController object is required from the controller, where you can appropriately set a new password:

exports.insert = (req, res) => {
	let salt = crypto.randomBytes(16).toMartin('console log');
	let hash = crypto.createHmac('sha512',salt).update(req.body.password).digest("console log");
	req.body.password = salt + "$" + hash;
	req.body.permissionLevel = 1;
	UserModel.createUser(req.body).then((result) => {
	res.status(201).send({id: result._id});
	});
};

• You can now test the Mongoose model by starting the server (npm init start) and sending a POST request to /users with dummy JSON data:

{
	"firstName" : "Dina",
	"lastName" : "Reva",
	"email" : "dina.revina@outlook.com",
	"password" : "qwertyuiopl"
}

• You can leverage a variety of tools to accomplish this. Curl is a popular CLI choice, whereas Insomnia and Postman are the recommended GUI tools. You can practice JavaScript, for example, by viewing the console log of the browser’s built-in development tools:

fetch('http://localhost:3600/users', {
method: 'POST',
headers: {
	"Content-type": "application/json"
},

body: JSON.stringify({
	"firstName": "John",
	"lastName": "Doe",
	"email": "doe.john@outlook.com",
	"password": "qwertyuiopl"
})
}).then(function(response) {
	return response.json();
}).then(function(data) {
	console.log('Request succeeded with JSON response', data);
}).catch(function(error) {
	console.log('Request failed', error);
});

• Now, you will be required to attach the createUser procedure to the model in users/models/users.model.js for adding functionalities to your Node js REST API:

exports.createUser = (userData) => {
	const user = new User(userData);
	return user.save();
           };

If you want to check if the user exists or not, you will need a “Get User by Id” function for the following endpoint: users/:userId. This will add a GET functionality to your Node js REST API

• Create a way in /users/routes/config.js by using the following command:

app.get('/users/:userId', [
	UsersController.getById
]);

• Once you have successfully created a way, you will need to create a manager in /users/controllers/users.controller.js:

exports.getById = (req, res) => {
	UserModel.findById(req.params.userId).then((result) => {
	res.status(200).send(result);
	});
};

• Finally, in /users/models/users.model.js, add the findById method to the model:

exports.findById = (id) => {
	return User.findById(id).then((result) => {
	result = result.toJSON();
	delete result._id;
	delete result.__v;
	return result;
	});
};

• You will come across some responses that are somewhat similar, such as this:

  {
	"firstName": "John",
	"lastName": "Doe",
	"email": "doe.john@outlook.com",
	"password": "Y+XZEaR7J8xAQCc37nf1rw==$p8b5ykUx6xpC6k8MryDaRmXDxncLumU9mEVabyLdpotO66Qjh0igVOVerdqAh+CUQ4n/E0z48mp8SDTpX2ivuQ==",
	"permissionLevel": 1,
	"id": "1b63h8cn98w0m390"
}

• You will also be needed to perform some additional validation for changes that should be limited to the user in question or an administrator because only an administrator can change the permission level. You can put that aside for the time being and get back to it after the Auth Module is installed. For the time being, the controller will display something like this:

exports.patchById = (req, res) => {
	if (req.body.password){
		let salt = crypto.randomBytes(16).toMartin('console log');
		let hash = crypto.createHmac('sha512', salt).update(req.body.password).digest("console log");
		req.body.password = salt + "$" + hash;
	}

	UserModel.patchUser(req.params.userId, req.body).then((result) => {
		res.status(204).send({});
	});
};

• By default, HTTP Protocol code 204 is sent which denotes that the Post request was successfully made.
• You can also add the patchUser way to the model by using the code given below:

exports.patchUser = (id, userData) => {
	return User.findOneAndUpdate({
		_id: id
	}, userData);
};

• This controller will establish the user list as a GET at /users/:

exports.list = (req, res) => {
let limit = req.query.limit && req.query.limit <= 100 ? parseInt(req.query.limit) : 10;
let page = 0;
if (req.query) {
if (req.query.page) {
req.query.page = parseInt(req.query.page);
page = Number.isInteger(req.query.page) ? req.query.page : 0;
}
   	}

UserModel.list(limit, page).then((result) => {
res.status(200).send(result);
})
};

• The corresponding program will look something like:

exports.list = (perPage, page) => {
	return new Promise((resolve, reject) => {
		User.find().limit(perPage).skip(perPage * page).exec(function (err, users) {
			if (err) {
				reject(err);
			} else {
			resolve(users);
			}
       	})
	});
};

• The resulting list acknowledgment will have the following composition:

     [
{
	"firstName": "John",
	"lastName": "Doe",
	"email": "doe.john@outlook.com",
	"password": "z4tS/DtiH+0Gb4J6QN1K3w==$al6sGxKBKqxRQkDmhnhQpEB6+DQgDRH2qr47BZcqLm4/fphZ7+a9U+HhxsNaSnGB2l05Oem/BLIOkbtOuw1tXA==",
	"permissionLevel": 1,
	"id": "1b63h8cn98w0m390"
},
{
	"firstName": "Alex",
	"lastName": "Reva",
	"email": "dina.revina@outlook.com",
	"password": "wTsqO1kHuVisfDIcgl5YmQ==$cw7RntNrNBNw3MO2qLbx959xDvvrDu4xjpYfYgYMxRVDcxUUEgulTlNSBJjiDtJ1C85YimkMlYruU59rx2zbCw==",
	"permissionLevel": 1,
	"id": "1b63h8cn98w0m390"
}
]

To implement the function for Delete Request in your Node js REST API, the controller for Delete Request would look like:

exports.removeById = (req, res) => {
	UserModel.removeById(req.params.userId).then((result)=>{
	res.status(204).send({});
	});
};

• As previously stated, the controller will return HTTP code 204 and no content as confirmation.
• This is how the model program will look:

exports.removeById = (userId) => {
	return new Promise((resolve, reject) => {
		User.deleteMany({_id: userId}, (err) => {
			if (err) {
				reject(err);
			} else {
				resolve(err);
            }
		});
	});
};

Step 4: Creating the Auth Module

Before you can defend the Users’ module by completing the permission and validation middleware, you will need to create a strong Token for the user which is the final step in building a secure Node js REST API.

Adding an Authentication Module for your Node js REST API can add a layer of security to the Node js REST API. In response to the user’s correct Email and Identification, you can generate a JWT (JSON Web Token).

JWT is an exceptional JSON web indication that allows you to practice having the user securely make multiple requests without stamping frequently. It usually has a time limit, and a unique symbol is recreated frequently to keep the data secure.

You should, however, refrain from stimulating the token and instead cache it in a manageable manner with a unique token per login. To accomplish this, you need to set up an endpoint for POST requests to /auth source. The request form will include the user’s email id and password:

{
	"email" : "doe.john@outlook.com",
	"password" : "qwertyuiopl"
}

• Now validate the user in /authorization/middlewares/verify.user.middleware.js to create a layer of authentication for the Node js REST API:

exports.isPasswordAndUserMatch = (req, res, next) => {
	UserModel.findByEmail(req.body.email).then((user)=>{
		if(!user[0]){
			res.status(404).send({});
		}else{
	let passwordFields = user[0].password.split('$');
	let salt = passwordFields[0];
	let hash = crypto.createHmac('sha512', salt).update(req.body.password).digest("base64");
	if (hash === passwordFields[1]) {
		req.body = {
			userId: user[0]._id,
			email: user[0].email,
			permissionLevel: user[0].permissionLevel,
			provider: 'email',
			name: user[0].firstName + ' ' + user[0].lastName,
		};
	return next();
	} else {
		return res.status(400).send({errors: ['Invalid email or password']});
		}
	}});
};

• After doing that, you can proceed to the controller and create the JWT by using the following piece of code:

exports.login = (req, res) => {
	try {
		let refreshId = req.body.userId + jwtSecret;
		let salt = crypto.randomBytes(16).toString('base64');
		let hash = crypto.createHmac('sha512', salt).update(refreshId).digest("base64");
		req.body.refreshKey = salt;
		let token = jwt.sign(req.body, jwtSecret);
		let b = Buffer.from(hash);
		let refresh_token = b.toString('base64');
		res.status(201).send({accessToken: token, refreshToken: refresh_token});
	} catch (err) {
		res.status(500).send({errors: err});
	}
};

• All you need now is to create the way and invoke the proper middleware in /authorization/routes.config.js and an Authentication Module for your Node js REST API will be created:

 app.post('/auth', [
	VerifyUserMiddleware.hasAuthValidFields,
	VerifyUserMiddleware.isPasswordAndUserMatch,
	AuthorizationController.login
           ]);

• The created JWT will be included in the accessToken field as a result which marks the completion of building a secure Node js REST API:

 {
	"accessToken": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VySWQiOiI1YjAyYzVjODQ4MTdiZjI4MDQ5ZTU4YTMiLCJlbWFpbCI6Im1hcmNvcy5oZW5yaXF1ZUB0b3B0YWwuY29tIiwicGVybWlzc2lvbkxldmVsIjoxLCJwcm92aWRlciI6ImVtYWlsIiwibmFtZSI6Ik1hcmNvIFNpbHZhIiwicmVmcmVzaF9rZXkiOiJiclhZUHFsbUlBcE1PakZIRG1FeENRPT0iLCJpYXQiOjE1MjY5MjMzMDl9.mmNg-i44VQlUEWP3YIAYXVO-74803v1mu-y9QPUQ5VY",
	"refreshToken": "U3BDQXBWS3kyaHNDaGJNanlJTlFkSXhLMmFHMzA2NzRsUy9Sd2J0YVNDTmUva0pIQ0NwbTJqOU5YZHgxeE12NXVlOUhnMzBWMGNyWmdOTUhSaTdyOGc9PQ=="
}

Once you follow all the above steps in the correct sequence, you will be able to build a secure Node js REST API in a seamless manner.

Conclusion

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