nestjs

NestJS Best Practices

NestJS is a powerful framework for building scalable Node.js applications. Adhering to these guidelines ensures your projects are maintainable, performant, and secure.

1. Code Organization and Structure

Adopt a feature-based, semi-hexagonal architecture. Each business domain gets its own module.

✅ GOOD: Feature-based Modules

Organize code by feature, not by type.

// src/modules/users/users.module.ts
@Module({
  controllers: [UsersController],
  providers: [UsersService, UsersRepository],
  exports: [UsersService],
})
export class UsersModule {}
// src/modules/users/controllers/users.controller.ts
// src/modules/users/services/users.service.ts
// src/modules/users/repositories/users.repository.ts
// src/modules/users/dtos/create-user.dto.ts

❌ BAD: Type-based Flat Structure

Avoid scattering related logic across different top-level folders.

// src/controllers/users.controller.ts
// src/services/users.service.ts

Naming Conventions

Follow standard TypeScript conventions for clarity:

• Files/Folders: kebab-case (e.g., user-profile.module.ts)
• Classes: PascalCase (e.g., UsersService, CreateUserDto)
• Interfaces: IPascalCase (e.g., IUserRepository)
• Functions/Methods: camelCase (e.g., createUser, findAllUsers)
• Constants: UPPER_SNAKE_CASE (e.g., JWT_SECRET)

2. Type Safety and Strictness

Always use explicit types. Avoid any. Enable strict TypeScript in tsconfig.json.

✅ GOOD: Explicit Types

Every variable, parameter, and return value must have an explicit type.

interface IUser { id: string; name: string; email: string; }
async function fetchUserById(id: string): Promise<IUser | null> {
  const user: IUser | undefined = await this.userRepository.findOne(id);
  return user ?? null;
}

❌ BAD: Implicit any

Leads to runtime errors and defeats TypeScript's purpose.

function fetchUserById(id) { // id is implicitly 'any'
  const user = this.userRepository.findOne(id);
  return user;
}