1. Introduction to Express.js Framework
Express.js is a widely-used, minimalist web application framework for Node.js, designed to build scalable, fast, and robust web applications. It provides an abstraction over the underlying HTTP module of Node.js, making it easier to manage routes, handle requests and responses, and implement middleware for a smooth development process.
2. Why Use Express.js?
1. Simplifies Web Development: Express.js abstracts complex server-side processes, providing a simple API to handle web requests and responses.
2. Lightweight and Fast: It has a minimal core but is extensible with a vast collection of middleware for additional features.
3. Middleware Support: Allows developers to implement functions that process requests at different stages, enhancing flexibility.
4. Routing Capabilities: Provides powerful routing options to manage multiple URL paths effectively.
5. Full Control Over Application Logic: Unlike opinionated frameworks, Express.js lets you structure your application the way you prefer.
3. Key Features of Express.js
1. Robust Routing System:
Offers a flexible way to define routes for different HTTP methods like GET, POST, PUT, and DELETE.
Example:
app.get('/home', (req, res) => {
res.send('Welcome to the Home Page');
});
2. Middleware Integration:
Middleware functions can process requests before reaching the final route handler.
Example:
app.use((req, res, next) => {
console.log(`Request URL: ${req.url}`);
next();
});
3. Error Handling:
Express allows custom error-handling middleware to catch and manage errors gracefully.
Example:
app.use((err, req, res, next) => {
console.error(err.stack);
res.status(500).send('Something went wrong!');
});
4. Installing and Setting Up Express.js
To use Express.js, you need Node.js and NPM installed. Follow these steps to set up Express in your project:
Install Express.js:
npm install express
Create a Basic Server:
const express = require('express');
const app = express();
app.get('/', (req, res) => {
res.send('Hello, Express!');
});
app.listen(3000, () => {
console.log('Server is running on http://localhost:3000');
});
5. Understanding How Express Works
1. Request and Response:
app.get('/api', (req, res) => {
res.json({ message: 'API Endpoint Working!' });
});
2. Routing Basics:
app.get('/about', (req, res) => {
res.send('About Us Page');
});
app.post('/submit', (req, res) => {
res.send('Form Submitted');
});
3. Middleware in Action:
app.use(express.json());
app.post('/data', (req, res) => {
res.send(`Data received: ${JSON.stringify(req.body)}`);
});