Installation & CLI

Introduction

Every great application starts with a solid foundation. The Nest CLI is your primary tool for scaffolding projects, generating components, and maintaining consistency across your codebase. Understanding the CLI workflow will save you hours of boilerplate writing.

Key Concepts

• Nest CLI: A command-line tool for generating and managing NestJS projects
• Scaffold: Auto-generated project structure with configuration files
• Bootstrap: The process of initializing and starting the application
• NestFactory: The core class that creates application instances

Real World Context

In production teams, consistency is paramount. The CLI ensures every developer generates modules, services, and controllers with the same structure. This eliminates debates about file naming, folder structure, and boilerplate patterns.

Deep Dive

Installing the CLI

bash
npm i -g @nestjs/cli

Creating a New Project

bash
nest new my-api

The CLI prompts you to choose a package manager (npm, yarn, or pnpm) and scaffolds:

my-api/
├── src/
│   ├── app.controller.ts
│   ├── app.module.ts
│   ├── app.service.ts
│   └── main.ts
├── test/
├── nest-cli.json
├── package.json
└── tsconfig.json

Bootstrapping the Application

The entry point is main.ts:

typescript
import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  await app.listen(process.env.PORT ?? 3000);
}
bootstrap();

Essential CLI Commands

Common Pitfalls

1. Not using --watch in development: Running nest start without --watch means you restart manually on every change. Always use nest start --watch or npm run start:dev.
2. Installing CLI locally only: Install globally (npm i -g) for easy access to nest commands anywhere. Local installation works but requires npx nest prefix.
3. Ignoring the nest-cli.json configuration: This file controls compilation, asset copying, and monorepo settings. Misconfiguring it breaks builds.

Best Practices

• Use the shorthand: nest g mo users instead of nest generate module users
• Generate related files together: nest g resource users creates module, controller, service, and DTOs
• Keep main.ts minimal: Configuration belongs in modules, not the bootstrap file
• Use environment variables for port: process.env.PORT ?? 3000 enables cloud deployment

Summary

The Nest CLI accelerates development by scaffolding projects and generating components with consistent structure. The NestFactory.create() method bootstraps your application by building the dependency graph from AppModule. Master the CLI commands to maintain velocity as your project grows.

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  await app.listen(process.env.PORT ?? 3000);
}
bootstrap();