First steps

In this set of articles, you'll learn the core fundamentals of Nest. To get familiar with the essential building blocks of Nest applications, we'll build a basic CRUD application with features that cover a lot of ground at an introductory level.

Language

We're in love with TypeScript, but above all - we love Node.js. That's why Nest is compatible with both TypeScript and pure JavaScript. Nest takes advantage of the latest language features, so to use it with vanilla JavaScript we need a Babel compiler.

We'll mostly use TypeScript in the examples we provide, but you can always switch the code snippets to vanilla JavaScript syntax (simply click to toggle the language button in the upper right hand corner of each snippet).

Prerequisites

Please make sure that Node.js (version >= 20) is installed on your operating system.

Setup

Setting up a new project is quite simple with the Nest CLI. With npm installed, you can create a new Nest project with the following commands in your OS terminal:

$ npm i -g @nestjs/cli
$ nest new project-name

info Hint To create a new project with TypeScript's stricter feature set, pass the --strict flag to the nest new command.

The project-name directory will be created, node modules and a few other boilerplate files will be installed, and a src/ directory will be created and populated with several core files.

<div class="file-tree">
  <div class="item">src</div>
  <div class="children">
    <div class="item">app.controller.spec.ts</div>
    <div class="item">app.controller.ts</div>
    <div class="item">app.module.ts</div>
    <div class="item">app.service.ts</div>
    <div class="item">main.ts</div>
  </div>
</div>

Here's a brief overview of those core files:

The main.ts includes an async function, which will bootstrap our application:

@@filename(main)


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

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

To create a Nest application instance, we use the core NestFactory class. NestFactory exposes a few static methods that allow creating an application instance. The create() method returns an application object, which fulfills the INestApplication interface. This object provides a set of methods which are described in the coming chapters. In the main.ts example above, we simply start up our HTTP listener, which lets the application await inbound HTTP requests.

Note that a project scaffolded with the Nest CLI creates an initial project structure that encourages developers to follow the convention of keeping each module in its own dedicated directory.

info Hint By default, if any error happens while creating the application your app will exit with the code 1. If you want to make it throw an error instead disable the option abortOnError (e.g., NestFactory.create(AppModule, {{ '{' }} abortOnError: false {{ '}' }})).

<app-banner-courses></app-banner-courses>

Platform

Nest aims to be a platform-agnostic framework. Platform independence makes it possible to create reusable logical parts that developers can take advantage of across several different types of applications. Technically, Nest is able to work with any Node HTTP framework once an adapter is created. There are two HTTP platforms supported out-of-the-box: express and fastify. You can choose the one that best suits your needs.

Whichever platform is used, it exposes its own application interface. These are seen respectively as NestExpressApplication and NestFastifyApplication.

When you pass a type to the NestFactory.create() method, as in the example below, the app object will have methods available exclusively for that specific platform. Note, however, you don't need to specify a type unless you actually want to access the underlying platform API.

const app = await NestFactory.create<NestExpressApplication>(AppModule);

Running the application

Once the installation process is complete, you can run the following command at your OS command prompt to start the application listening for inbound HTTP requests:

$ npm run start

info Hint To speed up the development process (x20 times faster builds), you can use the SWC builder by passing the -b swc flag to the start script, as follows npm run start -- -b swc.

This command starts the app with the HTTP server listening on the port defined in the src/main.ts file. Once the application is running, open your browser and navigate to http://localhost:3000/. You should see the Hello World! message.

To watch for changes in your files, you can run the following command to start the application:

$ npm run start:dev

This command will watch your files, automatically recompiling and reloading the server.

Linting and formatting

CLI provides best effort to scaffold a reliable development workflow at scale. Thus, a generated Nest project comes with both a code linter and formatter preinstalled (respectively eslint and prettier).

info Hint Not sure about the role of formatters vs linters? Learn the difference here.

To ensure maximum stability and extensibility, we use the base eslint and prettier cli packages. This setup allows neat IDE integration with official extensions by design.

For headless environments where an IDE is not relevant (Continuous Integration, Git hooks, etc.) a Nest project comes with ready-to-use npm scripts.

# Lint and autofix with eslint
$ npm run lint

# Format with prettier
$ npm run format