NestJS code explainers

typescript

import {
  WebSocketGateway,
  WebSocketServer,
  SubscribeMessage,

Building a real-time chat gateway in NestJS

websockets real-time socket.io

Intermediate 8 steps

typescript

import { IsInt, IsOptional, Max, Min } from 'class-validator';
import { Type } from 'class-transformer';
 
export class PaginationQueryDto {

Type-safe pagination queries in NestJS

pagination validation dto

Intermediate 7 steps

typescript

import {
  Injectable,
  NestInterceptor,
  ExecutionContext,

A per-route timeout interceptor in NestJS

interceptors metadata reflection rxjs

Intermediate 8 steps

typescript

import { Controller, Get, Param, Post, Body, Version, VERSION_NEUTRAL } from '@nestjs/common';
import { UsersService } from './users.service';
import { CreateUserDto } from './dto/create-user.dto';

How API versioning works in NestJS

api-versioning routing dependency-injection

Intermediate 9 steps

typescript

import { HttpService } from '@nestjs/axios';
import { Injectable, Logger, ServiceUnavailableException } from '@nestjs/common';
import { AxiosError } from 'axios';
import { catchError, firstValueFrom, retry, timer } from 'rxjs';

Resilient payment retries in NestJS

retry exponential-backoff rxjs

Advanced 8 steps

typescript

import { Injectable, NotFoundException } from '@nestjs/common';
import { EventEmitter2, OnEvent } from '@nestjs/event-emitter';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';

Decoupling side effects with NestJS events

event-driven decoupling dependency-injection

Intermediate 7 steps

typescript

import { Controller, Get, Param, StreamableFile, Res, NotFoundException, Header } from '@nestjs/common';
import { Response } from 'express';
import { createReadStream, promises as fsp } from 'fs';
import { join } from 'path';

Streaming CSV file downloads in NestJS

file-streaming http-headers error-handling

Intermediate 7 steps

typescript

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

Liveness vs readiness probes in NestJS

health-checks dependency-injection observability

Intermediate 6 steps

typescript

import {
  Controller,
  Post,
  Headers,

Verifying Stripe webhooks in NestJS

webhooks signature-verification event-handling

Intermediate 7 steps

typescript

import { Processor, WorkerHost, OnWorkerEvent } from '@nestjs/bullmq';
import { Logger } from '@nestjs/common';
import { Job } from 'bullmq';
import { MailerService } from '../mailer/mailer.service';

Processing background email jobs in NestJS

job-queue background-processing dependency-injection

Intermediate 7 steps

typescript

import { DynamicModule, Module, Provider } from '@nestjs/common';
import Redis, { RedisOptions } from 'ioredis';
 
export const REDIS_CLIENT = Symbol('REDIS_CLIENT');

Building a dynamic Redis module in NestJS

dependency-injection dynamic-modules provider-tokens

Intermediate 8 steps

typescript

import { Injectable, Scope, Inject } from '@nestjs/common';
import { REQUEST } from '@nestjs/core';
import { Request } from 'express';

Request-scoped context service in NestJS

dependency-injection request-scope immutability

Intermediate 8 steps

typescript

import {
  ArgumentsHost,
  Catch,
  ExceptionFilter,

A catch-all exception filter in NestJS

error-handling exception-filter http

Intermediate 8 steps

typescript

import { Module, Injectable } from '@nestjs/common';
import { ConfigModule, ConfigService } from '@nestjs/config';
import * as Joi from 'joi';

Validated, typed config in NestJS

configuration validation dependency-injection

Intermediate 6 steps

typescript

import {
  createParamDecorator,
  ExecutionContext,
  UnauthorizedException,

Building a @CurrentUser decorator in NestJS

decorators authentication request-context

Intermediate 6 steps

typescript

import {
  CanActivate,
  ExecutionContext,
  Injectable,

Role-based route guards in NestJS

authorization decorators metadata-reflection

Intermediate 8 steps

typescript

import {
  CanActivate,
  ExecutionContext,
  Injectable,

A rate-limiting guard in NestJS

rate-limiting guards metadata

Intermediate 7 steps

typescript

import { Injectable, Logger } from '@nestjs/common';
import { Cron, CronExpression } from '@nestjs/schedule';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository, LessThan } from 'typeorm';

Scheduled session cleanup in NestJS

cron-scheduling background-jobs repository-pattern

Intermediate 7 steps