Express.js: The Complete Guide

Are you a developer looking for a powerful and flexible web application framework? Look no further than Express.js. In this guide, we will cover everything you need to know to get started with this versatile and highly customizable tool.

Introduction to Express.js

Express.js is a popular web application framework for Node.js that makes it easy to create robust and scalable web applications. It provides a minimalist approach to web development and allows developers to build web applications with a simple and intuitive API.

Getting Started with Express.js

To get started with Express.js, you need to have Node.js and NPM installed on your system. Once you have these installed, you can use NPM to install Express.js by running the following command: npm install express

Creating an Express.js Application

Creating an Express.js application is easy. First, create a new Node.js project using NPM. Then, create a new file named app.js and add the following code:

1const express = require('express')
2const app = express()
3
4app.get('/', (req, res) => {
5  res.send('Hello World!')
6})
7
8app.listen(3000, () => {
9  console.log('Example app listening on port 3000!')
10})

This code creates a new Express.js application that listens for requests on port 3000 and responds with "Hello World!" when a request is made to the root path.

Routing in Express.js

Routing in Express.js allows you to define how your application responds to different HTTP requests. To define a new route, use the app.get() method as shown below:

1app.get('/about', (req, res) => {
2  res.send('About page')
3})

This code creates a new route that responds to requests to the /about path with the string "About page".

Middleware in Express.js

Middleware in Express.js allows you to modify the request and response objects before they are handled by your application. Middleware can be used for a variety of purposes, such as authentication, logging, and error handling.

To use middleware in your application, use the app.use() method as shown below:

1app.use((req, res, next) => {
2  console.log('Request received at', Date.now())
3  next()
4})

This code creates a middleware function that logs the time when a request is received and then passes control to the next middleware function or route handler.

Templating in Express.js

Templating in Express.js allows you to dynamically generate HTML pages using data from your application. Express.js supports a variety of templating engines, including EJS, Handlebars, and Pug.

To use a templating engine in your application, you first need to install it using NPM. Then, you can set it as the default engine for your application using the app.set() method as shown below:

1const express = require('express')
2const app = express()
3
4app.set('view engine', 'ejs')

This code sets EJS as the default templating engine for the application.

Conclusion

Express.js is a powerful and flexible web application framework that allows developers to create robust and scalable web applications with ease. Whether you're building a simple web app or a complex enterprise application, Express.js has everything you need to get the job done.