Building RESTful APIs with NestJS: A Step-by-Step Guide

NestJS, a progressive Node.js framework, has become a popular choice for building efficient, scalable, and enterprise-grade server-side applications. It leverages TypeScript and incorporates elements of object-oriented programming, functional programming, and reactive programming, making it a versatile tool for modern web development. In this guide, powered by Saigon Digital, we’ll walk you through the steps to build a RESTful API using NestJS.

Why Choose NestJS?

Before diving into the steps, let’s briefly explore why NestJS is a solid choice for building RESTful APIs:

TypeScript Integration: NestJS is built with TypeScript, offering type safety and robust tooling.
Modular Architecture: It promotes a modular structure, enhancing the maintainability and scalability of your application.
Dependency Injection: NestJS comes with a powerful Dependency Injection (DI) system, simplifying the management of your application’s dependencies.

Extensive Ecosystem: It has a rich ecosystem with a vast array of modules for database integration, authentication, and more.

Setting Up the Development Environment

Step 1: Install Node.js and NestJS CLI

Ensure you have Node.js installed on your machine. You can download it from Node.js.Next, install the NestJS CLI globally:

Step 2: Create a New NestJS Project

Create a new NestJS project using the CLI:

Step 3: Generate a Module

Modules in NestJS are used to organise your application.Let’s generate a module for our API:

Step 4: Create a Controller

Controllers handle incoming requests and return responses to the client.Generate a controller for your users module:

Step 5: Define Routes in the Controller

Open the users.controller.ts file and define the RESTful routes:

Step 6: Create a Service

Services contain the business logic of your application.Generate a service for the users module:Implement the business logic in users.service.ts:

Step 7: Inject the Service into the Controller

Modify the users.controller.ts to use the service:

About Saigon Digital

Saigon Digital is a leading digital agency specialising in web development, SEO, UI/UX design, and digital marketing. With a focus on delivering high-quality, innovative solutions, Saigon Digital empowers businesses to thrive in the digital age. Whether you're a startup or an established enterprise, Saigon Digital has the expertise to help you succeed. For more information, visit Saigon Digital.

NestJS implementation at Saigon Digital Case Studies

At Saigon Digital, we successfully launch our first project using NestJS as RESTful API name Visa Hotel Now and BVIS

Here what we did to leverage Visa Hotel Now implementing NestJS as Server Application

RESTful API Setup

Authentication and Authorisation

In NestJS, guards are a powerful feature used to control the flow of request processing, particularly useful for implementing authentication and authorization. Guards determine whether a request should be processed by the route handler or denied based on custom logic.Create AdminAuthGuard class to check authenticationCall AdminAuthGuard inside NestJS uses UseGuards Decorator function. UseGuards is a function in NestJS, it can be imported fromnestjs/common

Get current user with custom decorator

When using UseGuards, we can get current user and any RESTful API using custom decorator

Create a paramDecorator callback

Any RESTful API implementing AuthGuards we can import this User decorator by using it at @User decorator

Uploaded File

Uploading files is a common feature in many web applications, and NestJS provides a robust way to handle file uploads. This functionality is typically implemented using the @nestjs/common package, which integrates with Multer, a middleware for handling multipart/form-data primarily used for uploading files.

Create a controller to handle file upload requests. Use the @UseInterceptors decorator along with the FileInterceptor provided by @nestjs/platform-express.

Create a S3 service to handling upload file to AWS S3 bucket

Create a images service to handling additional logic. Then we can use these service in upload controller.

The Future of Saigon Digital with NestJS

As the digital landscape continues to evolve, Saigon Digital remains at the forefront of innovation by leveraging cutting-edge technologies to deliver exceptional solutions for its clients. One such technology that is shaping the future of Saigon Digital is NestJS, a progressive Node.js framework that is revolutionizing the way we build scalable and efficient server-side applications.

Conclusion

By following these steps, you’ve set up a basic RESTful API using NestJS. This guide covers the essentials, but NestJS offers many more features and capabilities to explore. You can integrate with databases, add authentication, handle validation, and much more to create a robust, production-ready API.

NestJS's modular architecture and TypeScript integration make it an excellent choice for building scalable and maintainable server-side applications. Start experimenting with more features and dive deeper into the official NestJS documentation to enhance your application furtherReady to elevate your project's API capabilities? Schedule a call with Saigon Digital today and let’s turn your vision into reality.