Heldinhow/nestjs-api

NestJS API Development

Overview

NestJS is a progressive Node.js framework for building scalable, enterprise-grade applications using TypeScript. This skill should be invoked when creating enterprise Node.js APIs, microservices, or backend applications that require strong architecture, dependency injection, and modular organization.

Core Principles

• Modular Architecture: Organize code into modules that encapsulate related functionality
• Dependency Injection: Leverage NestJS's built-in DI container for loose coupling
• Decorator-Based: Use decorators for routing, validation, and authentication
• TypeScript First: Benefit from full TypeScript support with static typing

Preparation Checklist

• [ ] Initialize NestJS project: nest new project-name
• [ ] Plan module structure (users, products, orders, etc.)
• [ ] Choose database integration (TypeORM, Prisma, Mongoose)
• [ ] Decide on validation approach (class-validator, built-in pipes)

Step-by-Step Process

1. Initialize: Create new NestJS project
2. Generate Modules: Use CLI to create modules: nest g module users
3. Create Components: Generate controllers and services
4. Configure DI: Set up providers and injections
5. Add Validation: Implement validation pipes for request bodies
6. Integrate Database: Connect TypeORM/Prisma for data persistence

Do's and Don'ts

• ✅ Do use the CLI for generating components to maintain convention
• ✅ Do keep business logic in services, not controllers
• ✅ Do use guards for authorization and interceptors for logging
• ❌ Don't put all logic in one module - loses architectural benefits
• ❌ Don't skip validation - always validate incoming data
• ❌ Don't ignore exception filters for consistent error handling

Anti-Patterns

• The Monolith Module: Putting everything in a single module
• Logic in Controllers: Adding business logic directly in controller methods
• Missing Error Handling: Not implementing global exception filters
• No Validation: Accepting user input without validation pipes