Express.js

Express.js (or simply Express) is a minimal and flexible Node.js web framework that provides a robust set of features for building server-side applications and RESTful APIs. It’s one of the most popular backend frameworks in Web Development, especially in the MERN stack (MongoDB, Express, React, Node.js).

Website: https://expressjs.com/

Express sits on top of Node.js, simplifying tasks like routing, middleware handling, and request/response management, which would otherwise require writing low-level code using Node’s built-in HTTP module. It integrates seamlessly with databases like MongoDB and PostgreSQL for full-stack development.

Features

• Middleware System: Provides a modular way to handle requests, responses, and errors.
• Routing: Simple and powerful URL routing for handling HTTP methods and paths.
• Template Engines: Supports rendering dynamic HTML using engines like EJS, Pug, or Handlebars.
• Static Files: Easily serve static assets like images, CSS, and JavaScript files.
• Integration Ready: Works with ORMs like Sequelize, Mongoose, or query builders like Knex.js.
• Lightweight and Unopinionated: Gives developers full control over structure and architecture.

Usage Example

Basic Server Setup

import express from 'express';
const app = express();
 
app.get('/', (req, res) => {
  res.send('Hello, Express.js!');
});
 
app.listen(3000, () => console.log('Server running on http://localhost:3000'));

Connecting to PostgreSQL (using pg)

import express from 'express';
import pkg from 'pg';
const { Pool } = pkg;
 
const app = express();
const pool = new Pool({ connectionString: process.env.DATABASE_URL });
 
app.use(express.json());
 
app.post('/users', async (req, res) => {
  const { name, email } = req.body;
  const result = await pool.query(
    'INSERT INTO users (name, email) VALUES ($1, $2) RETURNING *',
    [name, email]
  );
  res.json(result.rows[0]);
});
 
app.listen(5000, () => console.log('Server running on port 5000'));

Advantages

• Simple, fast, and lightweight to build scalable APIs
• Large ecosystem with a huge number of middleware packages
• Perfect fit for single-page apps and RESTful services
• Works seamlessly with frontends built in React, Angular, or Vue
• Easily integrates with databases, authentication, and cloud services

Limitations

• Minimal structure — requires manual setup for large-scale projects
• Lacks built-in support for advanced features (e.g., ORM, validation, security) — must rely on third-party middleware
• Performance may lag behind specialized frameworks in high-load environments

Purpose

Express.js is ideal for building REST APIs, backend services, or microservices quickly and efficiently. It strikes a perfect balance between simplicity and flexibility, making it the go-to choice for JavaScript-based backend development.