Express.js

Express.js: A Powerful Web Application Framework for Node.js 🚀

Express.js is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications. It's designed for building single-page, multi-page, and hybrid web applications.

Why Use Express.js? 🤔

• Fast and minimalist web framework

• Easy to set up and configure

• Large community and extensive plugin ecosystem

• Flexible routing system

• Supports various templating engines

Installation and Basic Setup 🛠️

To install Express.js, run the following command in your project directory:

npm install express

Here's a basic example of an Express.js application:

const express = require('express');
const app = express();
const port = 3000;

app.get('/', (req, res) => {
  res.send('Hello World!');
});

app.listen(port, () => {
  console.log(`Example app listening at <http://localhost>:${port}`);
});

Key Features of Express.js 🔑

• Routing

• Middleware support

• Template engine integration

• Static file serving

• Error handling

Types of Applications Using Express.js 🌐

• RESTful APIs

• Single-page applications (SPAs)

• E-commerce platforms

• Real-time applications (with Socket.io)

• Content management systems (CMS)

Core Concepts of Express.js 🧠

Here's a diagram illustrating the core concepts of Express.js:

Key Functions in Express.js 🛠️

• express(): Creates an Express application

• app.use(): Mounts middleware

• app.get(), app.post(), app.put(), app.delete(): HTTP method routing

• app.all(): Handles all HTTP methods

• app.param(): Adds callback triggers to route parameters

• res.send(): Sends a response

• res.json(): Sends a JSON response

• res.render(): Renders a view template

Advanced Topics in Express.js 🚀

1. Middleware Chaining

app.use((req, res, next) => {
  console.log('Time:', Date.now());
  next();
});

2. Error Handling Middleware

app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).send('Something broke!');
});

3. Template Engines

app.set('view engine', 'pug');
app.get('/', (req, res) => {
  res.render('index', { title: 'Hey', message: 'Hello there!' });
});

4. Database Integration

const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/myapp', {useNewUrlParser: true, useUnifiedTopology: true});

5. Authentication Middleware

const auth = (req, res, next) => {
  if (req.session && req.session.userId) {
    return next();
  } else {
    return res.sendStatus(401);
  }
};

app.get('/profile', auth, (req, res) => {
  res.send('Profile Page');
});

By mastering these concepts and features, you can build robust and efficient web applications with Express.js. 💪