NestJS Flashcards

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NestJS is a progressive Node.js framework for building efficient, reliable, and scalable server-side applications. Built with TypeScript and heavily inspired by Angular's architecture, NestJS provides a solid architectural foundation using proven design patterns like dependency injection, decorators, and modules. It supports both REST and GraphQL APIs out of the box and integrates seamlessly with popular libraries like Express and Fastify. NestJS is designed for enterprise-level applications, offering features like built-in testing utilities, microservices support, WebSocket integration, and extensive documentation. Its modular structure and TypeScript-first approach make it an excellent choice for large-scale applications that require maintainability and testability.

Our flashcard app contains carefully selected NestJS interview questions, complete with comprehensive answers, to effectively prepare you for any interview requiring NestJS knowledge. IT Flashcards is not only a valuable tool for job seekers but also a great way to strengthen and test your understanding of NestJS framework. Regular practice with the app will keep you updated with the latest trends in Node.js backend development and enhance your expertise in building enterprise-grade applications.

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NestJS

What is NestJS and what is it used for?

NestJS is a framework for building efficient, reliable, and scalable server-side applications. It is known for its modular architecture, which promotes solid programming practices and adheres to object-oriented, functional, and functional-reactive programming principles.

With NestJS, developers can create various types of server-side applications, such as traditional web applications, microservices, GraphQL applications, WebSocket applications, and many more.

NestJS is built on **Express.js** (a popular Node.js framework) and is compatible with a wide range of other libraries, such as **TypeORM**, **Sequelize**, **Mongoose**, etc.

Additionally, NestJS leverages the latest TypeScript features, but is also compatible with plain JavaScript.

In summary, NestJS is a comprehensive and flexible framework for building server-side applications, promoting good programming practices and enabling the creation of reliable, efficient applications.

NestJS

What design patterns are natively used in NestJS?

NestJS utilizes many popular design patterns in line with good programming practices. The most important ones are:

1. **Dependency Injection** - NestJS relies on an IoC (Inversion of Control) engine, which allows for effective dependency management and promotes SOLID principles. All service classes, controllers, etc., can be easily injected into other classes, facilitating testing and application development.

2. **Module Pattern** - NestJS promotes a modular code writing style, where entire applications are divided into smaller, more manageable modules. Each module can encompass its own services, controllers, middleware, etc. This allows for high scalability and easy code maintenance.

3. **Decorator Pattern** - NestJS, like Angular, heavily utilizes decorators, which are a pivotal feature of TypeScript. Decorators allow for adding metadata to classes, methods, etc., enhancing code readability and maintainability.

4. **Observer Pattern** - NestJS supports reactive programming using the RxJS library. This allows for easy creation of asynchronous operations and data streams.

In summary, NestJS leverages many proven design patterns, contributing to its effective and scalable approach to building server-side applications.

NestJS

What is a module used for in NestJS?

**Module** in NestJS is a key element for organizing code. Modules group related elements, such as **controllers**, **providers**, and other **modules**. A module allows structuring an application and promotes the principles of **Single Responsibility Principle** and **Loose Coupling Principle**.

A **module** in NestJS is a class decorated with the **@Module()** decorator. This decorator accepts an object in JSON format that can contain the keys `imports`, `controllers`, `providers`, and `exports`.

An example module definition might look like this:

import { Module } from '@nestjs/common';
import { CatsController } from './cats.controller';
import { CatsService } from './cats.service';

@Module({
  controllers: [CatsController],
  providers: [CatsService],
  exports: [CatsService]
})
export class CatsModule {}

In the above example, we declare the `CatsModule`, which includes the `CatsController` and `CatsService`. The service is also exported, allowing it to be used in other modules that import the `CatsModule`.

NestJS

How do you define a controller in NestJS?

Definition of a controller in NestJS begins with the **@Controller()** decorator, which is an integral part of every controller in NestJS. In addition to the decorator, a controller consists of a set of defined endpoint methods. Each method is responsible for handling a specific HTTP request (GET, POST, DELETE, etc.) to a specified endpoint.

Example of a controller definition in NestJS:

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

@Controller('books')
export class BooksController {
  @Get()
  findAll() {
    return "This action returns all books";
  }
}

In the above example, the controller named `BooksController` handles the `/books` endpoint. The `findAll` method is decorated by **@Get()** and handles GET requests to the `/books` endpoint.

Each controller should ideally correspond to one business segment of the application (such as managing books, users, etc.) and contain appropriate methods for that segment.

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