Getting Started with Nest.js

Nest is a framework for building efficient, scalable Node.js server-side applications. It uses progressive JavaScript, is built with TypeScript (preserves compatibility with pure JavaScript) and combines elements of OOP (Object Oriented Programming), FP (Functional Programming), and FRP (Functional Reactive Programming).

Nest is a framework for building efficient, scalable Node.js server-side applications. It uses progressive JavaScript, is built with TypeScript (preserves compatibility with pure JavaScript) and combines elements of OOP (Object Oriented Programming), FP (Functional Programming), and FRP (Functional Reactive Programming).

If you have ever worked on a Node.js application before, either built a REST API or an enterprise application, you must have realised how tedious and daunting it was to maintain, especially whenever the application start to scale. The more you add new features to the application, the larger the codebase.

Table of Contents

Creating a proper structure for such application can result into serious headache if not properly managed, especially as a result of application specific configurations. This is why Nest.js was created.
Nest.js was built mainly to eliminate disorganized codebases and give Node.js application a moderate and reasonable structure out of the box. Heavily inspired by Angular, Nest.js was built with TypeScript and uses Express.js under hood. This rightly makes it compatible with the majority of express middleware.

In this post, I will introduce and take you through the process of getting started with Nest.js. You will learn about several ways to install the framework on your machine and why you need to consider using it for your next project. In the process of doing this, you will create a very simple RESTful API that enables users to fetch, create and delete books in a bookstore.

This is a very simple application but yet broad enough to give you comprehensive insight on how to craft an application with Nest.js.


Familiarity with TypeScript and a reasonable knowledge of JavaScript will help you get the best out of this tutorial. Experienced with building applications with Angular will be a plus but not a requirement as the article will give you a proper guide on how to easily begin.

You need to install Node and npm. It is advisable to also install nodemon globally on your machine.

Overview of Nest.js and why use it

Nest.js is a server-side Node.js framework for building efficient, reliable and scalable applications. Built by Kamil and backed by quite a number of reputable organizations and individuals.

Creating a proper structure for such application can result into serious headache if not properly managed, especially as a result of application specific configurations. This is why Nest.js was created.
Fully built with TypeScript, it comes with the benefits of code type checking and dependency injection which helps to facilitate the process of development of applications. If you are conversant with the structure of Angular applications, you are going to feel so comfortable with the key concepts of Nest.js and getting started with it will be quite an easy task. Anyways, this post will provide you with the required details needed to start building applications with Nest.js.

In addition, the following list shows some of the benefits of Nest.js as explained here by Kamil:

Now that you have been briefed about this awesome framework, let’s take a look at the building blocks of Nest.js.

Building blocks of Nest.js

The following are the building blocks used when building Nest.js applications:


Typical to most web frameworks, controllers in Nest.js are responsible for handling any incoming requests and returning responses to the client side of the application. For example, if you make an API call to a particular endpoint, say /home, the controller will receive this request and based on the available resources, it will returned the appropriate response.

Nest.js was structured in a way that the routing mechanism is able to control which controller will be responsible for handling a particular request.

Defining a basic controller in Nest.js is as good as creating a TypeScript file and including a decorator @Controller() just like the code snippet below:

  // users.controller.ts 

import { Controller, Get } from '@nestjs/common';

export class UsersController {
 findAll() { 
   return 'This will return all the users';

The prefix of users within the Controller decorator will prompt the UsersController to handle any /users GET request within an application and return the appropriate response as specified. Other HTTP request handled by the controller includes POST , PUT, DELETE as we will see later in the tutorial.

Once a controller is created, it needs to be added to the module definition before Nest.js can easily recognise it. This could be the root ApplicationModule or any other module created within the application. More about this in the module section of this post.


As mentioned earlier, Nest.js was heavily inspired by Angular and similar to an Angular application, one can easily create a provider and inject it into controllers or other providers too as well. These providers are also called services and based on the philosophy of Nest.js, it was designed to abstract any form of complexity and logic to a class called service.

A service provider in Nest.js is just a normal JavaScript class with a special @Injectable() decorator at the top.

For example, you can simply create a service to fetch users as shown below:

    // users.service.ts

import { Injectable } from '@nestjs/common';
import { User } from './interfaces/user.interface';

export class UsersService {
  private readonly users: User[] = [];

  create(user: User) { 
    this.users.push(user);   }

  findAll(): User[] {
    return this.users;

The provider created above is a class with two methods create() and findAll(), which can be used to create and return all users respectively. And to easily help with type checking an interface was used to specify the type of elements that should be received by the methods.


Modules are more like the most important basic building block in Nest.js. They are TypeScript files decorated with @Module decorator. This attached decorator provides metadata that Nest makes use of to organize the application structure. With modules you can easily group related files into one.

Each Nest.js application must have at least one module, usually referred to as the root module. This root module is the top-level module and usually enough for a small application but it is advisable to break a large application into multiple modules as it helps to maintain the structure of the application.

If you have an application that manages a lot of data or functionality about users , we can group both the controller, services and other related files into a single module, say UsersModule for example:

import { Module } from '@nestjs/common';
import { UsersController } from './users.controller.ts';
import { UsersService } from './users.service.ts';

  controllers: [UsersController],
  providers: [UsersService]

export class UsersModule {}

From the preceding file, we are exported a UsersModule that contains both the UsersController and UsersService. With this in place, we can then proceed to import and use the UsersModule within the root module of the application as shown in the following code snippet:

import { UsersModule } from './users/users.module';


export class AppModule { }

Other important concepts


Data transfer object is an object that defines how data will be sent over the network.


TypeScript interfaces are used for type-checking and defining the types of data that can be passed to a controller or a Nest service.

Dependency injection

Dependency injection is a design pattern used to increase efficiency and modularity of applications. It is often used by the biggest frameworks to keep code clean and easier to use. Nest.js also makes use of it to basically create coupled components.

With this pattern, it is very easy to manage dependencies between building blocks like controllers, providers and modules. The only thing required is to define the dependency for example a UsersService() in the constructor of a controller as shown here:

export class UsersController {
constructor(private readonly usersService: UsersService){}

With some of these concepts briefly covered, you can now proceed to the next section, where you will put all the knowledge gained so far in this post into use as you will learn how to seamlessly build a RESTful API using Nest.js.

What you will build with Nest.js

As stated earlier in this post, you will create a sample application that will help you get a good grasp on some of the core concepts of Nest.js.

This application will be specifically for a bookstore. At the end of the post you would have created a micro-service that will enable users to create and add a new book with few descriptions to an existing list of books. This could be from a database, but to ensure simplicity in this post, we won’t really be connecting our application to a database yet. But instead, we will make use of a mock data of books and once a new book is created, we will push and add it to the list.

Installing Nest.js

In order to easily scaffold a new Nest.js application, you will need to globally installed Nest CLI. It is a command line interface tool specifically created to amongst other things, help to craft a new Nest.js app in no time and provide access to ( built in generators ) several commands to generate different files and produce a well-structured application.

Apart from using the CLI tool, you can also install a new Nest.js application by cloning the starter project from GitHub using Git, but for the purpose of this tutorial run the following command to install the Nest CLI:

npm i -g @nestjs/cli

This will give you access to the nest command for project installation and other project specific commands.

Next, run the command below to install a new project named bookstore-nest within your development folder:

nest new bookstore-nest

You will be asked few questions during the installation, just follow the prompt and respond accordingly. Next, once the installation is complete, change directory into the newly created project and start the application with:

// change directory
cd bookstore-nest

// start the application
npm run start

or better still, run the command below in order to use Nodemon for the project:

// start the application using nodemon
npm run start:dev

Navigate to http://localhost:3000 from your favorite browser, you will see the Hello World! message as shown here:

Generate a module

First you will start by generating a module for the bookstore. To do this, you will leverage the inbuilt file generator using Nest CLI. Run the following command to scaffold a new module for the application:

nest generate module books

The command above will create a new folder named books within the src folder. Also within the books folder you will find a books.module.ts file.

// ./src/books/books/module.ts

import { Module } from '@nestjs/common';
export class BooksModule {}

This was generated by the command and the module has also been added to the app.module.ts which happens to be the root module of the application.

Create routes

Next, you will create routes for the endpoints. As mentioned earlier, routes are in controllers, so you need to create controllers that will handle individual endpoints. Again, use Nest CLI to generate your controllers, run the following command:

nest generate controller books

This will create a controller inside the books folder. Since we won’t really be connecting to the database for now, create a sample mock data for the bookstore. Under the src folder, create a subfolder named mocks and within the newly created folder, create a new TypeScript file named books.mock.ts and paste the following code in it:

// ./src/mocks/books.mock.ts
export const BOOKS = [
    { id: 1, title: 'First book', description: "This is the description for the first book", author: 'Olususi Oluyemi' },
    { id: 2, title: 'Second book', description: "This is the description for the second book", author: 'John Barry' },
    { id: 3, title: 'Third book', description: "This is the description for the third book", author: 'Clement Wilfred' },
    { id: 4, title: 'Fourth book', description: "This is the description for the fourth book", author: 'Christian nwamba' },
    { id: 5, title: 'Fifth book', description: "This is the description for the fifth book", author: 'Chris anderson' },
    { id: 6, title: 'Sixth book', description: "This is the description for the sixth book", author: 'Olususi Oluyemi' },

Setting up service

Next, you will create a service to hold all the logic for the bookstore. Run the following command to generate a service:

nest generate service books

This command will create a new file named books.service.ts within ./src/books folder.

Get books

Next, open the newly created file and paste the following:

//  ./src/books/books.service.ts

  import { Injectable, HttpException } from '@nestjs/common';
  import { BOOKS } from '../mocks/books.mock';

  export class BooksService {
      books = BOOKS;

      getBooks(): Promise<any> {
          return new Promise(resolve => {
      getBook(bookID): Promise<any> {
          let id = Number(bookID);
          return new Promise(resolve => {
              const book = this.books.find(book => === id);
              if (!book) {
                  throw new HttpException('Book does not exist!', 404);

First, you imported the requires modules from Nest.js and also BOOKS from the mock data you created earlier.

Next, you created two different methods named getBooks() and getBook() to retrieve the list of books from the mock data and to fetch just one book using the bookID as a parameter.

Add book

Next, add the method below to the /src/books/books.service.ts immediately after the getBook() method:

//  ./src/books/books.service.ts

import { Injectable, HttpException } from '@nestjs/common';
import { BOOKS } from '../mocks/books.mock';
export class BooksService {
    books = BOOKS;
    addBook(book): Promise<any> {
        return new Promise(resolve => {

The method above will be used to push a new book to the existing list

Delete book

Finally, add the last method to delete a particular book using the bookID as a parameter:

//  ./src/books/books.service.ts

import { Injectable, HttpException } from '@nestjs/common';
import { BOOKS } from '../mocks/books.mock';
export class BooksService {
    books = BOOKS;
    deleteBook(bookID): Promise<any> {
        let id = Number(bookID);
        return new Promise(resolve => {
            let index = this.books.findIndex(book => === id);
            if (index === -1) {
                throw new HttpException('Book does not exist!', 404);
            this.books.splice(1, index);

Inject service into controller

Here, you will use dependency injection design pattern to pass the BooksService into the BooksController through a constructor. Open the BooksController created earlier and paste the following code in it:

// ./src/books/books.controller.ts

import { Controller, Get, Param, Post, Body, Query, Delete } from '@nestjs/common';
import { BooksService } from './books.service';
import { CreateBookDTO } from './dto/create-book.dto';

export class BooksController {
    constructor(private booksService: BooksService) { }

    async getBooks() {
        const books = await this.booksService.getBooks();
        return books;

    async getBook(@Param('bookID') bookID) {
        const book = await this.booksService.getBook(bookID);
        return book;

    async addBook(@Body() createBookDTO: CreateBookDTO) {
        const book = await this.booksService.addBook(createBookDTO);
        return book;

    async deleteBook(@Query() query) {
        const books = await this.booksService.deleteBook(query.bookID);
        return books;

Here in this controller, first, the important modules were imported from @nestjs/common and you also import both the BooksService and CreateBookDTO respectively. CreateBookDTO is a data transfer object, a TypeScript class created for type-checking and to define the structures of what an object looks like when creating a new book. We will create this DTO in a bit.

Next, you used constructor to inject the BooksService into the controller and created four different methods which are:

Each of the methods has a special decorator attached to it, which makes it very easy to route each HTTP request to a specific method within the controller.


In the previous section, you made use of a data transfer object called CreateBookDTO. To set it up, navigate to the ./src/books folder and create a new subfolder name dto. Next, within the newly created folder, create another file and call it create-book.dto.ts and paste the following in it:

// ./src/books/dto/create-book.dto.ts

export class CreateBookDTO {
    readonly id: number;
    readonly title: string;
    readonly description: string;
    readonly author: string;

You are almost done with the application, the next line of action is to take a look at the BooksModule and update it accordingly. You will do that in the next section.

Update the books module

Navigate back to the BooksModule created earlier and update it with the code below:

// ./src/books/books.module.ts

import { Module } from '@nestjs/common';
import { BooksController } from './books.controller';
import { BooksService } from './books.service';
  controllers: [BooksController],
  providers: [BooksService]
export class BooksModule {}

Test the application

Start the application again if it is not running at the moment with:

npm run start

and use postman to test the API

Get Books

Get book using bookID

Create a new book

Delete a book


We have barely scratched the surface on what Nest.js has to offer the Node.js world in this post. To get more conversant with this awesome framework, first, we took a quick look at the fundamentals and basic building blocks of Nest.js and then proceeded to build a RESTful API where you also learnt about dependency injection amongst other things.

I hope this tutorial as given you enough information to try out Nest.js for your next application. Feel free to drop your thoughts in the comment section below and find the complete source code of this tutorial here on GitHub.

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Top 7 Most Popular Node.js Frameworks You Should Know

Top 7 Most Popular Node.js Frameworks You Should Know

Node.js is an open-source, cross-platform, runtime environment that allows developers to run JavaScript outside of a browser. In this post, you'll see top 7 of the most popular Node frameworks at this point in time (ranked from high to low by GitHub stars).

Node.js is an open-source, cross-platform, runtime environment that allows developers to run JavaScript outside of a browser.

One of the main advantages of Node is that it enables developers to use JavaScript on both the front-end and the back-end of an application. This not only makes the source code of any app cleaner and more consistent, but it significantly speeds up app development too, as developers only need to use one language.

Node is fast, scalable, and easy to get started with. Its default package manager is npm, which means it also sports the largest ecosystem of open-source libraries. Node is used by companies such as NASA, Uber, Netflix, and Walmart.

But Node doesn't come alone. It comes with a plethora of frameworks. A Node framework can be pictured as the external scaffolding that you can build your app in. These frameworks are built on top of Node and extend the technology's functionality, mostly by making apps easier to prototype and develop, while also making them faster and more scalable.

Below are 7of the most popular Node frameworks at this point in time (ranked from high to low by GitHub stars).


With over 43,000 GitHub stars, Express is the most popular Node framework. It brands itself as a fast, unopinionated, and minimalist framework. Express acts as middleware: it helps set up and configure routes to send and receive requests between the front-end and the database of an app.

Express provides lightweight, powerful tools for HTTP servers. It's a great framework for single-page apps, websites, hybrids, or public HTTP APIs. It supports over fourteen different template engines, so developers aren't forced into any specific ORM.


Meteor is a full-stack JavaScript platform. It allows developers to build real-time web apps, i.e. apps where code changes are pushed to all browsers and devices in real-time. Additionally, servers send data over the wire, instead of HTML. The client renders the data.

The project has over 41,000 GitHub stars and is built to power large projects. Meteor is used by companies such as Mazda, Honeywell, Qualcomm, and IKEA. It has excellent documentation and a strong community behind it.


Koa is built by the same team that built Express. It uses ES6 methods that allow developers to work without callbacks. Developers also have more control over error-handling. Koa has no middleware within its core, which means that developers have more control over configuration, but which means that traditional Node middleware (e.g. req, res, next) won't work with Koa.

Koa already has over 26,000 GitHub stars. The Express developers built Koa because they wanted a lighter framework that was more expressive and more robust than Express. You can find out more about the differences between Koa and Express here.


Sails is a real-time, MVC framework for Node that's built on Express. It supports auto-generated REST APIs and comes with an easy WebSocket integration.

The project has over 20,000 stars on GitHub and is compatible with almost all databases (MySQL, MongoDB, PostgreSQL, Redis). It's also compatible with most front-end technologies (Angular, iOS, Android, React, and even Windows Phone).


Nest has over 15,000 GitHub stars. It uses progressive JavaScript and is built with TypeScript, which means it comes with strong typing. It combines elements of object-oriented programming, functional programming, and functional reactive programming.

Nest is packaged in such a way it serves as a complete development kit for writing enterprise-level apps. The framework uses Express, but is compatible with a wide range of other libraries.


LoopBack is a framework that allows developers to quickly create REST APIs. It has an easy-to-use CLI wizard and allows developers to create models either on their schema or dynamically. It also has a built-in API explorer.

LoopBack has over 12,000 GitHub stars and is used by companies such as GoDaddy, Symantec, and the Bank of America. It's compatible with many REST services and a wide variety of databases (MongoDB, Oracle, MySQL, PostgreSQL).


Similar to Express, hapi serves data by intermediating between server-side and client-side. As such, it's can serve as a substitute for Express. Hapi allows developers to focus on writing reusable app logic in a modular and prescriptive fashion.

The project has over 11,000 GitHub stars. It has built-in support for input validation, caching, authentication, and more. Hapi was originally developed to handle all of Walmart's mobile traffic during Black Friday.

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Why learn Node.js?

Node.js uses JavaScript - a language known to millions of developers worldwide - thus giving it a much lower learning curve even for complete beginners. Using Node.js you can build simple Command Line programs or complex enterprise level web applications with equal ease. Node.js is an event-driven, server-side, asynchronous development platform with lightning speed execution. Node.js helps you to code the most complex functionalities in just a few lines of code...

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A Beginner Guide To Node.js (Basic Introduction To Node.js)

Node.js is a very popular javascript free and open source cross-platform for server-side programming built on Google Chrome’s Javascript V8 Engine. It is used by thousands of developers around the world to develop mobile and web applications. According to StackOverflow survey, Node.js is one of most famous choice for building the web application in 2018.


Node.js is a very popular javascript free and open source cross-platform for server-side programming built on Google Chrome’s Javascript V8 Engine. It is used by thousands of developers around the world to develop mobile and web applications. According to StackOverflow survey, Node.js is one of most famous choice for building the web application in 2018.

In this article, you will gain a deep understanding of node, learn how node.js works and why it is so popular among the developers and startups. Not In startup even big companies like eBay, Microsoft, GoDaddy, Paypal etc.

Why is Node.js so much popular

It is fast very fast

It’s a javascript runtime built on google chrome javascript v8 engine which means both node js and js executed in your browser running in the same engine that makes it very fast in comparison to any other server-side programming language.

It uses event-driven and non-blocking model

Node.js uses the event-driven, non-blocking I/O model that makes it very lightweight and efficient.
Now let’s understand the above statement in more details. Here I/O refers to Input /Output.

Event Driven Programming is a paradigm in which control flow of any program is determined by the occurrence of the events. All these events monitor by the code which is known as an event listener. If you are from javascript background then most probably you know what is event-listeners. In short, event-listener is a procedure or function that waits for an event to occurs. In javascript, onload, onclick, onblur most common event-listener.

**Blocking I/O **takes time and hence block other function. Consider the scenario where we want to fetch data from the database for two different users. Here we can not get the data of the second user until we did not complete the first user process. Since javascript is a single threaded and here we would have to start a new thread every time we want to fetch user data. So here Non-Blocking I/O parts come in.

Example of Blocking I/O operation

<span class="hljs-keyword">const</span> fs = <span class="hljs-built_in">require</span>(‘fs’);
<span class="hljs-keyword">var</span> contents = fs.readFileSync(<span class="hljs-string">'package.json'</span>).toString();
<span class="hljs-built_in">console</span>.log(contents);

In** Non-blocking I/O **operations, you can get the user2 data without waiting for the completion of the user1 request. You can initiate both requests in parallel. **Non-blocking I/O **eliminates the need for the multi-threaded, since the system can handle multiple requests at the same time. That is the main reason which makes it very fast.

Example of Non-blocking I/O operation

<span class="hljs-keyword">const</span> fs = <span class="hljs-built_in">require</span>(‘fs’);
fs.readFile(<span class="hljs-string">'package.json'</span>, <span class="hljs-function"><span class="hljs-keyword">function</span> (<span class="hljs-params">err, buf</span>)</span>{
    <span class="hljs-built_in">console</span>.log(buf.toString());

Note: You can learn more about the event loop and other things by going through this link.

What is Node Package Manager ( NPM )

It is is the official package manager for the node. It bundles automatically installed when you install node in your system. It is used to install new packages and manage them in useful ways. NPM install packages in two modes local and global. In the local mode, NPM installs packages in the node_module directory of the current working directory which location is owned by current user. Global packages installed in the directory where the node is installed and the location is owned by the root user.

What is the package.json

package.json is a plain JSON text file which manages all the packaged which you installed in your node application. Every Node.js applications should have this file at the root directory to describe the application metadata. A simple package.json file looks like below

    <span class="hljs-string">"name"</span> : <span class="hljs-string">"codesquery"</span>,
    <span class="hljs-string">"version"</span> : <span class="hljs-string">"1.0.0"'
    "repository": {
	"type" : "git",
	"url" : "github_repository_url"
    "dependencies": {
	"async": "0.8.0",
	"express": "4.2.x"

In the above file, name and versions are mandatory for the package.json file and rest is optional.

Installing Node.js

  • In Windows, you can install the node.js by using the installer provided by the official node.js website. Follow the installer instruction and node.js will be installed in your windows system.
  • In Linux OS, you can install the node.js by adding the PPA in your system and then install node js. Run the below command the terminal to install node js
sudo apt-get install curl python-software-properties
curl -sL https:<span class="hljs-comment">// | sudo -E bash -</span>
sudo apt-get install nodejs

  • In macOS, download the macOS installer from the official node.js website. Now run the installer by accepting the license and selecting the destination.

Test Node.js Installation

You can test the node.js installation by typing below command in the terminal

node -v

If node.js was installed successfully then you will see the installed version of the node in the terminal.

Frameworks and Tools

After gaining the popularity among the developers, there are so many frameworks built for the node js for the different type of uses. Here, I will tell you some of the most famous node js frameworks in the market

  • Express.js is the most popular framework for node.js development. A lot of popular websites is powered by express.js due to its lightweight.
  • Hapi.js is a powerful and robust framework for developing the API. This framework has features like input validation, configuration based functionality, error handling, caching and logging.
  • Metor.js is one of the most used frameworks in the node js web application development. This framework is backed by a huge community of developers, tutorials and good documentation.
  • is used to build a real-time web application like chat system and analytics. Its allow the bi-direction data flow between the web client and server.
  • Koa.js is yet another most used framework to build the web application using the node js. This framework is backed by the team behind Express.js. It allows you to ditch callbacks and increase error handling.


Today, Node.js shaping the future of web and application development technology. This is the just the basic of how node js works. If you want to build a scalable web application using the node js then you need to know more then this.

Till now, you have got the basic idea of node.js and now it is time to build something using the node.js. You can start with first by create a simple server using the node.js and then connect your node with MongoDB to perform the basic crud operation.