Functional middleware in NestJS - Mini Project: Build & Apply

Functional Middleware in NestJS

📖 Scenario: You are building a simple NestJS server that logs requests. Middleware helps you run code before your route handlers. Functional middleware is a simple function that can log info about each request.

🎯 Goal: Create a functional middleware in NestJS that logs the HTTP method and URL of each incoming request.

📋 What You'll Learn

Create a functional middleware function named loggerMiddleware

Use the req, res, and next parameters in the middleware

Log the HTTP method and URL using console.log

Call next() to pass control to the next middleware or route handler

Apply the middleware to a simple NestJS AppModule using configure method

💡 Why This Matters

🌍 Real World

Middleware is used in real web servers to handle tasks like logging, authentication, and error handling before requests reach the main logic.

💼 Career

Understanding functional middleware is essential for backend developers working with NestJS or similar frameworks to build scalable and maintainable server applications.

1

Create the functional middleware

Create a function called loggerMiddleware that takes req, res, and next as parameters.

NestJS

# Your code here
// Create the loggerMiddleware function with req, res, next parameters

Need a hint?

Middleware functions always have three parameters: req, res, and next.

2

Add logging inside the middleware

Inside the loggerMiddleware function, add a console.log statement that logs the HTTP method and URL from req.method and req.url. Then call next().

NestJS

function loggerMiddleware(req, res, next) {
  // Add console.log to show req.method and req.url
  // Call next() to continue
  // Your code here
}

Need a hint?

Use template strings to combine req.method and req.url in the log.

3

Apply middleware in AppModule

In the AppModule class, implement the configure method. Use consumer.apply(loggerMiddleware).forRoutes('*') to apply the middleware to all routes.

NestJS

function loggerMiddleware(req, res, next) {
  console.log(`Request: ${req.method} ${req.url}`);
  next();
}

import { Module, NestModule, MiddlewareConsumer } from '@nestjs/common';

@Module({})
export class AppModule implements NestModule {
  configure(consumer: MiddlewareConsumer) {
    // Apply loggerMiddleware to all routes
    // Your code here
  }
}

Need a hint?

The configure method receives a consumer to apply middleware.

4

Complete the NestJS server setup

Add the necessary imports for NestFactory from @nestjs/core. Create an async bootstrap function that creates the app with NestFactory.create(AppModule) and listens on port 3000. Call bootstrap().

NestJS

function loggerMiddleware(req, res, next) {
  console.log(`Request: ${req.method} ${req.url}`);
  next();
}

import { Module, NestModule, MiddlewareConsumer } from '@nestjs/common';
// Import NestFactory here

@Module({})
export class AppModule implements NestModule {
  configure(consumer: MiddlewareConsumer) {
    consumer.apply(loggerMiddleware).forRoutes('*');
  }
}

// Create async bootstrap function to start server
// Your code here

Need a hint?

Use await with NestFactory.create and app.listen inside an async function.