Lecture on NestJS and Building a CRUD REST API

Introduction to NestJS

• NestJS is a framework for building scalable Node.js web applications using TypeScript.
• The lecture will cover building a CRUD REST API using NestJS.
• Instructor: Vladimir, a full-stack software developer.
• The course aims to build a production-like app, including authentication and relational databases using Prisma, and end-to-end tests.

Teaching Approach

• Hands-on coding approach.
• Code will be available in a GitHub repository.
• Questions can be asked in the comment section or on the channel "Code with Vlad".
• Basic understanding of JavaScript ES6 and TypeScript is required but explanations will be provided step-by-step.

Overview of NestJS

What is NestJS?

• NestJS is a backend framework for Node.js that fully embraces TypeScript.
• It solves architectural problems encountered with Express.js by providing a structured way to build applications.
• Uses Express.js under the hood but adds significant abstractions.
• Emphasizes modularity and dependency injection.
• Often referred to as “Angular for the backend.”

Why Use NestJS?

• Structure: Provides a well-defined structure out of the box.
• Modularity: Encourages breaking down applications into modules.
• TypeScript Support: Built with TypeScript.
• Functionality: Integrates well with GraphQL, microservices, REST APIs, and has good documentation and security practices.
• Popularity: Rapidly growing and highly favored by employers due to its structured approach.

Getting Started

Prerequisites

• Node.js (version 16 or higher with long-term support).
• NestJS CLI installed globally via npm install -g @nestjs/cli.
• A code editor, preferably VS Code.

Creating a New Project

• Use the command nest new nest-js-api-tutorial to create a new project.
• Choose a package manager, e.g., Yarn.
• Structure provided by the CLI includes folders for sources and tests, and configuration files.

NestJS Concepts

Modules

• Core of the Application: Organize and structure an application by features or areas of functionality.
• Main Module: app.module.ts is the root module.
• Feature Modules: Create feature-specific modules like auth module, user module, bookmarks module, etc.

Creating Modules

• Classes annotated with the @Module decorator.
• Can import other modules, controllers, and providers.
• Feature modules example: Auth module for authentication logic, User module for user-related logic, Bookmarks module, and a Database module.

Controllers and Services

• Controllers: Handle incoming requests and return responses to the client.
• Services (Providers): Execute business logic and handle data-related tasks.
• Create controllers and services manually first to understand the structure before using CLI generators.

Dependency Injection and Decorators

Dependency Injection

• Allows passing instances of classes and services as dependencies.
• Example: Inject authService into the AuthController to handle authentication tasks.

Decorators in NestJS

• Simplify the definition and management of metadata and routes.
• Examples: @Post, @Get, @Body, @Param, @Controller, @Injectable.

Building the CRUD API

Authentication Service

• Implement login and signup functionalities using JWT (JSON Web Tokens).
• Hashing Passwords: Use argon2 for password hashing and comparison.
• JWT: Sign tokens with secrets and provide access tokens for client authentication.

Controllers and Routes

• Define routes for signup, login, and user-specific actions like fetching user info and updating user details.
• Protect routes using guards and strategies.
• Implement and use custom decorators for cleaner code.

Database Integration

Using Prisma ORM

• Prisma: A modern ORM for Node.js and TypeScript used for database abstraction and type-safe data handling.
• Setting Up Database: Configure a PostgreSQL database using Docker and Docker Compose.
• Schema Definition: Define models in Prisma schema file and generate migrations.
• Handling Models and Relationships: Define relationships and data models for users and bookmarks.

Applying Migrations and Seeding Data

• Migrations: Use Prisma migrate commands to push schema changes to the database.
• Seeding Data: Use custom scripts to seed initial development data.

Testing the Application

Types of Testing

• Unit Testing: Testing individual functions or methods, often using mocks for dependencies.
• Integration Testing: Testing multiple components together to ensure they work as expected.
• End-to-End (E2E) Testing: Testing the full flow of the application to simulate user interactions.

Implementing Tests with Jest and Pactum

• Setup Testing Environment: Configure Jest for end-to-end tests and resetting database state between test runs.
• Running Tests: Use Pactum to define and execute API tests, ensuring the application behaves as expected.
• Automating Tests: Setup scripts to automate running tests and managing test database.
• Validating Tokens and Auth: Test JWT token generation and validation for secure routes.

Performance and Security

• Optimize performance with clustering and proper resource management, potentially using PM2 for process management.
• Secure the API by validating inputs, handling errors correctly, and ensuring sensitive data is protected.

Conclusion

• The course demonstrated setting up a full-featured, secure, and scalable NestJS application.
• Covered the entire development lifecycle from setup, coding, database integration, testing, and optimization for production.
• Encourages exploration of advanced topics like further test automation and deploying NestJS applications.