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Learn Nestjs - 10 Code Examples & CST Typing Practice Test

NestJS is a progressive Node.js framework for building efficient, scalable, and maintainable server-side applications using TypeScript and modern JavaScript.

View all 10 Nestjs code examples →
NestJS Simple Counter APINestJS Hello World APINestJS Simple Todo APINestJS Query Params ExampleNestJS POST JSON ExampleNestJS Middleware ExampleNestJS Exception Filter ExampleNestJS Param ExampleNestJS Service Injection ExampleNestJS Async Service Example

Learn NESTJS with Real Code Examples

Updated Nov 25, 2025

Explain

NestJS leverages TypeScript to provide strong typing and modern OOP/FP paradigms for Node.js backend development.

It uses the modular architecture inspired by Angular, with controllers, providers, and modules.

Supports REST APIs, GraphQL, WebSockets, microservices, and more.

Encourages best practices like dependency injection, middleware, and exception handling.

Widely used for enterprise-grade Node.js applications and complex backend systems.

Core Features

Modules, controllers, and providers for structured development

Decorators for routing, DI, and metadata

Exception filters and pipes for validation and error handling

Middleware, guards, and interceptors for request/response management

Integration with databases via TypeORM, Prisma, and Mongoose

Basic Concepts Overview

Modules encapsulate features

Controllers handle routes

Providers implement business logic

Decorators annotate classes/methods with metadata

Dependency Injection manages service instantiation

Project Structure

src/ - source code

src/app.module.ts - root module

src/app.controller.ts - root controller

src/app.service.ts - root service

main.ts - bootstrap file

Building Workflow

Generate modules, controllers, and services via CLI

Implement routing and business logic

Integrate databases, middleware, and guards

Test endpoints and services

Deploy backend using Node.js or Docker

Difficulty Use Cases

Beginner: simple REST API

Intermediate: CRUD application with database

Advanced: GraphQL API with authentication

Expert: microservices architecture with messaging

Architect: enterprise-grade backend with scalability and testing

Comparisons

NestJS vs Express: structured + TypeScript vs minimalistic JS

NestJS vs Fastify: scalable + modular vs lightweight performance

NestJS vs Blazor: backend API vs full-stack C# SPA

NestJS vs Spring Boot: Node.js + TypeScript vs Java backend

NestJS vs Koa: DI and modules vs minimalistic middleware

Versioning Timeline

2017 - NestJS created by Kamil Myśliwiec

2018 - Nest CLI released, TypeScript-first adoption

2019-2020 - GraphQL, WebSocket, microservice support added

2021-2023 - Stability and adoption increase

2024-2025 - Continuous feature expansion and community growth

Glossary

Module: encapsulates related features

Controller: handles incoming requests

Provider: service or logic layer

Decorator: metadata for classes/methods

Pipe: request transformation/validation

Installation Setup

Install Node.js and npm

Install Nest CLI: `npm i -g @nestjs/cli`

Create project: `nest new project-name`

Install dependencies and start development server

Run `npm run start:dev` for hot reload

Environment Setup

Install Node.js and npm

Install Nest CLI

Create project and install dependencies

Set up TypeScript compiler

Run development server and hot reload

Config Files

nest-cli.json - CLI config

tsconfig.json - TypeScript config

package.json - dependencies and scripts

src/main.ts - bootstrap file

src/app.module.ts - root module

Cli Commands

nest new project-name

nest generate module users

nest generate controller users

nest generate service users

nest build/start

Internationalization

Use i18n packages for localization of messages

Translate error messages and logs

Format dates/numbers based on locale

Support multi-language APIs

Externalize all user-facing strings

Accessibility

Ensure APIs are consistent and well-documented

Handle errors gracefully with HTTP status codes

Provide clear and structured responses

Enable CORS and authentication where required

Follow API design best practices

Ui Styling

Not applicable; backend framework

Serve static assets if needed

Integrate with templating engines if required

API responses structured in JSON

Optionally render server-side templates (e.g., Handlebars, Pug)

State Management

Stateless HTTP request handling

Service-level shared state via DI

Use database or cache for persistent state

Message queues for event-driven state

Avoid in-memory mutable global state

Data Management

Integrate with relational/non-relational DB

Use ORMs like TypeORM or Prisma

Validate and transform input via Pipes

Serialize/deserialize JSON for APIs

Caching via Redis or in-memory services

Architecture

Modules -> organize related features

Controllers -> handle incoming requests

Providers -> services for business logic

Middlewares, Guards, Interceptors -> cross-cutting concerns

Decorators -> metadata-driven routing, validation, and DI

Rendering Model

Handles HTTP requests via controllers

Business logic in providers

Routing determined by decorators

Middlewares, guards, and interceptors for request processing

Supports microservice and WebSocket patterns

Architectural Patterns

Modular and layered design

Dependency Injection for service management

Use of decorators for metadata and routing

Separation of concerns (controllers vs services)

Supports event-driven and message-based architectures

Real World Architectures

Enterprise REST APIs with authentication and roles

GraphQL APIs for frontend apps

Microservices communicating via RabbitMQ/Kafka

WebSocket servers for real-time apps

Full-stack applications with Angular/React frontend

Design Principles

Modular architecture for scalability

Dependency Injection for maintainable code

Decorator-based metadata

Type-safe backend development

Integrations with modern backend ecosystems

Scalability Guide

Organize features into modules

Use microservices for distributed architecture

Leverage caching and database optimization

Horizontal scaling via load balancers

Optimize middleware and request processing

Migration Guide

Migrate from plain Express to NestJS by wrapping routes in controllers

Refactor services into providers

Leverage modules for feature encapsulation

Integrate DI for dependencies

Test all endpoints and business logic

Performance Notes

Leverages Node.js event loop for asynchronous tasks

Supports Fastify for high-performance HTTP

Scales horizontally with microservices

Optimized for TypeScript type safety

Minimal overhead compared to raw Express when structured properly

Security Notes

Use Guards for authentication/authorization

Validate requests with Pipes

Sanitize inputs to prevent injection attacks

Handle errors with Exception Filters

Secure APIs with HTTPS and tokens

Monitoring Analytics

Log requests and errors

Use metrics and tracing tools

Monitor performance via APM

Enable health checks for microservices

Integrate with monitoring dashboards (Prometheus/Grafana)

Code Quality

Follow TypeScript best practices

Use DI and modular design

Unit and integration tests

Lint and format consistently

Document APIs with Swagger

Practical Examples

Build a CRUD REST API

Implement JWT authentication

Create GraphQL resolver

Set up WebSocket chat server

Integrate a microservice with RabbitMQ

Troubleshooting

Check TypeScript compilation errors

Verify DI registration of providers

Ensure module imports are correct

Debug middleware and guard execution

Check runtime logs for exceptions

Testing Guide

Unit-test services and modules with Jest

Integration tests for controllers

E2E testing with Supertest

Mock dependencies using DI

Test guards, pipes, and interceptors

Deployment Options

Deploy Node.js backend to cloud (AWS, Azure, GCP)

Dockerize application

Use PM2 or Node process managers

Host REST/GraphQL APIs behind Nginx or reverse proxy

Integrate CI/CD pipelines

Tools Ecosystem

Nest CLI for scaffolding

Node.js runtime

TypeORM, Prisma, or Mongoose for databases

Jest for testing

Swagger integration for API documentation

Integrations

Database ORM/ODM (TypeORM, Prisma, Mongoose)

GraphQL (Apollo Server)

WebSockets (Socket.io)

Messaging queues (RabbitMQ, Kafka)

Third-party APIs and authentication services

Productivity Tips

Use Nest CLI for scaffolding

Reuse modules and providers

Leverage decorators for clean code

Write tests alongside features

Use TypeScript type-checking to prevent runtime errors

Challenges

Learning TypeScript and decorators

Structuring modules efficiently

Dependency Injection understanding

Testing complex services and controllers

Scaling backend architecture

Learning Path

Learn Node.js and TypeScript basics

Understand NestJS modules, controllers, and providers

Practice building REST APIs

Learn authentication, GraphQL, and WebSockets

Build a full-featured scalable backend

Skill Improvement Plan

Week 1: NestJS basics, simple REST API

Week 2: Services and database integration

Week 3: Authentication and authorization

Week 4: GraphQL and WebSockets

Week 5: Microservices and deployment

Interview Questions

What is NestJS and why use it?

Explain modules, controllers, and providers.

How does DI work in NestJS?

How to handle validation and exceptions?

How to implement GraphQL or microservices in NestJS?

Cheat Sheet

@Controller - define routes

@Get/@Post - define HTTP method handlers

@Injectable - mark services for DI

Modules - organize features

Providers - implement business logic

Books

NestJS - A Progressive Node.js Framework

Mastering NestJS

Building Enterprise Applications with NestJS

Full-Stack TypeScript with NestJS and Angular

Advanced Node.js with NestJS

Tutorials

Build a CRUD REST API

Add authentication with JWT

Implement GraphQL resolvers

Set up WebSocket chat server

Deploy NestJS with Docker

Official Docs

https://docs.nestjs.com/

https://github.com/nestjs/nest

Community Links

NestJS GitHub

StackOverflow NestJS questions

Discord & Reddit communities

YouTube tutorials

NestJS blog posts

Community Support

NestJS GitHub

StackOverflow

Discord & Reddit communities

NestJS official docs

YouTube and blog tutorials

Monetization

Enterprise backend solutions

API-based SaaS platforms

Real-time applications (chat, trading, dashboards)

Subscription services using NestJS backend

Backend for mobile and web apps

Future Roadmap

Expanded support for serverless and edge computing

Enhanced microservice orchestration

Better GraphQL integration

Improved CLI and tooling

Stronger ecosystem and community contributions

When Not To Use

Small scripts or lightweight APIs

Projects that don’t use TypeScript

Apps where raw Express/Fastify is sufficient

Highly experimental projects needing minimal abstraction

Frontend-only projects

Final Summary

NestJS is a TypeScript-first Node.js framework for backend development.

Uses modular architecture, DI, and decorators for scalable apps.

Supports REST, GraphQL, WebSockets, and microservices.

Strong TypeScript integration ensures maintainability.

Ideal for enterprise-grade, scalable server-side applications.

Faq

Is NestJS free?

Yes - open-source under MIT license.

Does it replace Express?

NestJS uses Express/Fastify under the hood with abstraction.

Which languages are used?

TypeScript and modern JavaScript.

Is it suitable for enterprise apps?

Yes, designed for scalable and maintainable systems.

Can it handle microservices?

Yes, built-in support for microservice architecture and messaging.

Code Sample Descriptions

1

NestJS Simple Counter API

import { Controller, Get, Post } from '@nestjs/common';
import { Module } from '@nestjs/common';
import { NestFactory } from '@nestjs/core';

class CounterService {
    private count = 0;
    getCount() { return this.count; }
    increment() { this.count++; return this.count; }
    decrement() { this.count--; return this.count; }
    reset() { this.count = 0; return this.count; }
}

@Controller('counter')
class CounterController {
    constructor(private readonly service: CounterService) {}
    @Get() getCount() { return { count: this.service.getCount() }; }
    @Post('increment') increment() { return { count: this.service.increment() }; }
    @Post('decrement') decrement() { return { count: this.service.decrement() }; }
    @Post('reset') reset() { return { count: this.service.reset() }; }
}

@Module({ controllers: [CounterController], providers: [CounterService] })
class AppModule {}

async function bootstrap() {
    const app = await NestFactory.create(AppModule);
    await app.listen(3000);
    console.log('NestJS server running on http://localhost:3000');
}
bootstrap();

Demonstrates a simple NestJS REST API with a counter using a service and controller.

Let’s Try →
2

NestJS Hello World API

import { Controller, Get } from '@nestjs/common';
import { Module } from '@nestjs/common';
import { NestFactory } from '@nestjs/core';

@Controller()
class AppController {
    @Get() hello() { return { message: 'Hello World' }; }
}

@Module({ controllers: [AppController] })
class AppModule {}

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

A basic NestJS REST API returning 'Hello World'.

Let’s Try →
3

NestJS Simple Todo API

import { Controller, Get, Post, Body } from '@nestjs/common';
import { Module } from '@nestjs/common';
import { NestFactory } from '@nestjs/core';

class TodoService {
    private todos: string[] = [];
    getAll() { return this.todos; }
    add(todo: string) { this.todos.push(todo); return todo; }
}

@Controller('todos')
class TodoController {
    constructor(private readonly service: TodoService) {}
    @Get() getTodos() { return this.service.getAll(); }
    @Post() addTodo(@Body('todo') todo: string) { return this.service.add(todo); }
}

@Module({ controllers: [TodoController], providers: [TodoService] })
class AppModule {}

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

A minimal Todo REST API with in-memory storage.

Let’s Try →
4

NestJS Query Params Example

import { Controller, Get, Query } from '@nestjs/common';
import { Module } from '@nestjs/common';
import { NestFactory } from '@nestjs/core';

@Controller('greet')
class GreetController {
    @Get() hello(@Query('name') name: string) { return { message: `Hello ${name || 'Guest'}` }; }
}

@Module({ controllers: [GreetController] })
class AppModule {}

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

An API endpoint demonstrating query parameter usage.

Let’s Try →
5

NestJS POST JSON Example

import { Controller, Post, Body } from '@nestjs/common';
import { Module } from '@nestjs/common';
import { NestFactory } from '@nestjs/core';

@Controller('echo')
class EchoController {
    @Post() echo(@Body() data: any) { return data; }
}

@Module({ controllers: [EchoController] })
class AppModule {}

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

A POST endpoint receiving JSON data and returning it.

Let’s Try →
6

NestJS Middleware Example

import { Injectable, NestMiddleware, Module } from '@nestjs/common';
import { NestFactory } from '@nestjs/core';
import { Request, Response, NextFunction } from 'express';

@Injectable()
class LoggerMiddleware implements NestMiddleware {
    use(req: Request, res: Response, next: NextFunction) {
        console.log(`${req.method} ${req.url}`);
        next();
    }
}

@Module({})
class AppModule {
    configure(consumer) {
        consumer.apply(LoggerMiddleware).forRoutes('*');
    }
}

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

Shows how to use middleware to log requests in NestJS.

Let’s Try →
7

NestJS Exception Filter Example

import { ExceptionFilter, Catch, ArgumentsHost, HttpException, Module } from '@nestjs/common';
import { NestFactory } from '@nestjs/core';
import { Controller, Get } from '@nestjs/common';

@Catch(HttpException)
class HttpErrorFilter implements ExceptionFilter {
    catch(exception: HttpException, host: ArgumentsHost) {
        const ctx = host.switchToHttp();
        const response = ctx.getResponse();
        response.status(exception.getStatus()).json({ message: exception.message });
    }
}

@Controller()
class AppController {
    @Get('error') throwError() { throw new HttpException('Custom error', 400); }
}

@Module({ controllers: [AppController] })
class AppModule {}

async function bootstrap() {
    const app = await NestFactory.create(AppModule);
    app.useGlobalFilters(new HttpErrorFilter());
    await app.listen(3000);
}
bootstrap();

A custom exception filter catching HTTP errors.

Let’s Try →
8

NestJS Param Example

import { Controller, Get, Param, Module } from '@nestjs/common';
import { NestFactory } from '@nestjs/core';

@Controller('users')
class UserController {
    @Get(':id') getUser(@Param('id') id: string) { return { id, name: `User ${id}` }; }
}

@Module({ controllers: [UserController] })
class AppModule {}

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

An endpoint demonstrating route parameters.

Let’s Try →
9

NestJS Service Injection Example

import { Injectable, Controller, Get, Module } from '@nestjs/common';
import { NestFactory } from '@nestjs/core';

@Injectable()
class HelloService { getMessage() { return 'Hello from Service'; } }

@Controller()
class AppController {
    constructor(private readonly helloService: HelloService) {}
    @Get() hello() { return { message: this.helloService.getMessage() }; }
}

@Module({ controllers: [AppController], providers: [HelloService] })
class AppModule {}

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

Demonstrates dependency injection of a service into a controller.

Let’s Try →
10

NestJS Async Service Example

import { Injectable, Controller, Get, Module } from '@nestjs/common';
import { NestFactory } from '@nestjs/core';

@Injectable()
class AsyncService {
    async fetchData() { return new Promise(resolve => setTimeout(() => resolve('Async Data'), 500)); }
}

@Controller()
class AppController {
    constructor(private readonly service: AsyncService) {}
    @Get('data') async getData() { return { data: await this.service.fetchData() }; }
}

@Module({ controllers: [AppController], providers: [AsyncService] })
class AppModule {}

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

Shows a service returning data asynchronously using Promises.

Let’s Try →

Frequently Asked Questions about Nestjs

What is Nestjs?

NestJS is a progressive Node.js framework for building efficient, scalable, and maintainable server-side applications using TypeScript and modern JavaScript.

What are the primary use cases for Nestjs?

Building RESTful APIs and GraphQL services. Creating microservices with built-in support. Developing server-side applications with TypeScript. Implementing real-time WebSocket applications. Building enterprise-grade backend systems

What are the strengths of Nestjs?

Strong typing with TypeScript ensures code reliability. Highly modular and scalable architecture. Integration with modern backend tools and frameworks. Supports enterprise-level patterns and practices. Comprehensive documentation and strong community support

What are the limitations of Nestjs?

Steeper learning curve for developers unfamiliar with TypeScript or Angular-style patterns. Adds abstraction over raw Node.js/Express APIs. Some advanced features require understanding of decorators and DI. Initial setup may feel heavy for small projects. Less flexible than lightweight frameworks like Fastify/Express for simple apps

How can I practice Nestjs typing speed?

CodeSpeedTest offers 10+ real Nestjs code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.

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