Introduction to Express.js

Express.js, or simply Express, is a back end web application framework for Node.js, released as free and open-source software under the MIT License. It is designed for building web applications and APIs.

Key Features

• Fast: Light-weight and unopinionated. It adds minimal overhead to Node.js features.
• Middleware: A robust system for extending functionality.
• Routing: Powerful ways to define URL structures and handle HTTP methods.
• Performance: Because it's just a thin layer over Node, it inherits its blazing speed.

The Philosophical Approach

Express is "unopinionated." This means it doesn't force you into a specific project structure or require you to use specific databases or template engines. You are free to choose the modules that fit your needs.

Prerequisites

Before starting with Express, you should have a solid understanding of:

1. HTML/CSS: For basic web structure.
2. JavaScript (ES6+): Especially Promises and Async/Await.
3. Node.js Basics: Modules, NPM, and the HTTP module.

// First look at an Express app
const express = require('express');
const app = express();

app.get('/', (req, res) => {
  res.send('Welcome to the Express Masterclass!');
});

app.listen(3000);