Building custom middleware in Node.js - Mini Project: Build & Apply

Building custom middleware

📖 Scenario: You are creating a simple Node.js server using Express. You want to add a custom middleware function that logs the request method and URL for every incoming request.

🎯 Goal: Build a custom middleware function in Express that logs the HTTP method and URL of each request, then use it in your server.

📋 What You'll Learn

Create an Express app

Write a middleware function named logger that logs the request method and URL

Use the logger middleware in the Express app

Add a simple route / that sends a response

💡 Why This Matters

🌍 Real World

Middleware is used in real web servers to add features like logging, authentication, and error handling without changing route code.

💼 Career

Understanding middleware is essential for backend developers working with Node.js and Express to build scalable and maintainable web applications.

1

Set up Express app

Create a variable called express that requires the 'express' module. Then create a variable called app by calling express().

Node.js

const express = require('express');
const app = express();
// Your code here

Need a hint?

Use require('express') to import Express and call it to create the app.

2

Create logger middleware

Write a middleware function called logger that takes req, res, and next as parameters. Inside it, log the request method and URL using console.log, then call next().

Node.js

const express = require('express');
const app = express();

// Create logger middleware function
// Your code here

Need a hint?

The middleware function must call next() to pass control to the next middleware.

3

Use logger middleware in app

Use the logger middleware in the Express app by calling app.use(logger).

Node.js

const express = require('express');
const app = express();

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

// Use logger middleware
// Your code here

Need a hint?

Use app.use() to add middleware to the Express app.

4

Add a simple route

Add a GET route for / using app.get that sends the text 'Hello World' as the response.

Node.js

const express = require('express');
const app = express();

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

app.use(logger);

// Add GET / route
// Your code here

Need a hint?

Use app.get with a callback that calls res.send to send the response.