Node.js is an open-source, cross-platform, server-side runtime environment built on Chrome’s V8 JavaScript engine. It allows developers to write server-side applications in JavaScript, which was traditionally used only for client-side scripting in web browsers.

Express is a popular web application framework for Node.js, a platform for building server-side applications using JavaScript.

What is Express JS?

Express.js is a popular, open-source web application framework for Node.js, designed for building web applications and APIs. It provides a robust set of features for web and mobile applications, including middleware support, routing, and template engines.

Express.js is built on top of Node.js, and as such, it allows developers to take advantage of the non-blocking and event-driven nature of Node.js. It also provides a simple and intuitive API for building web applications, making it a popular choice for developers who want to build scalable and fast web applications.

Why Express JS?

There are several reasons why Express.js is a popular choice for building web applications in Node.js:

1. Simplicity: Express.js has a simple and intuitive API that makes it easy to build web applications and APIs. It provides a minimal set of features out-of-the-box, which allows developers to focus on building their application logic without getting bogged down in boilerplate code.
2. Flexibility: Express.js is a highly flexible framework that allows developers to customize and extend it to meet their specific needs. It provides a wide range of middleware and plugin modules that can be used to add additional functionality to an application.
3. Routing: Express.js has a powerful routing system that allows developers to define routes for different HTTP methods and URLs. This makes it easy to build RESTful APIs and web applications with clean and intuitive URLs.
4. Middleware: Express.js provides built-in support for middleware functions, which can be used to modify incoming requests and outgoing responses. This makes it easy to add functionality such as authentication, logging, and error handling to an application.
5. Large Community: Express.js has a large and active community of developers who contribute to its development, provide support, and create a wide range of plugins and middleware modules.

Overall, Express.js is a versatile and powerful framework that allows developers to build scalable and maintainable web applications and APIs with ease. Its simplicity, flexibility, routing, middleware support, and large community make it a popular choice for building web applications in Node.js.

Features of Express JS

Express.js is a feature-rich web application framework for Node.js, designed for building web applications and APIs. Some of the key features of Express.js include:

1. Middleware support: Express.js has built-in support for middleware functions, which can be used to modify incoming requests or outgoing responses. This allows developers to add functionality such as authentication, logging, and error handling to their applications.
2. Routing: Express.js provides a powerful routing system that allows developers to define routes for different HTTP methods and URLs. This makes it easy to build RESTful APIs and web applications with clean and intuitive URLs.
3. Template engines: Express.js supports several template engines, including EJS, Handlebars, and Pug, which makes it easy to build dynamic web pages and server-side rendered applications.
4. Error handling: Express.js has a robust error handling system that allows developers to handle errors in a centralized and consistent manner.
5. Built-in security features: Express.js provides built-in security features such as Cross-Site Request Forgery (CSRF) protection, HTTP parameter pollution prevention, and secure HTTP headers.
6. Session and cookie management: Express.js has built-in support for managing user sessions and cookies, which allows developers to implement user authentication and authorization in their applications.
7. File uploads: Express.js has built-in support for handling file uploads, making it easy to implement file upload functionality in web applications.
8. Middleware and plugin ecosystem: Express.js has a large and active community of developers who contribute to its development and create a wide range of middleware and plugin modules that can be used to extend its functionality.

Advantages of using Express JS with Node JS

1. Express allows developers to write server-side applications in JavaScript, which was traditionally used only for client-side scripting in web browsers.
2. Provides an event-driven architecture and non-blocking I/O API that allows it to handle a large number of requests simultaneously while keeping the server responsive and fast.
3. Simplifies the process of building web applications and APIs with a simple and intuitive API and a powerful routing system.
4. Provides built-in support for middleware functions, making it easy to add functionality such as authentication, logging, and error handling to an application.
5. Supports several template engines, making it easy to build dynamic web pages and server-side rendered applications.
6. Provides a robust error handling system that allows developers to handle errors in a centralized and consistent manner.
7. Has built-in security features such as Cross-Site Request Forgery (CSRF) protection and HTTP parameter pollution prevention.
8. Has a large and active community of developers who contribute to its development and create a wide range of plugins and middleware modules that can be used to extend its functionality.

Limitations of Express JS

While Express.js is a popular and powerful framework for building web applications and APIs with Node.js, it also has some limitations. Here are some of the limitations of Express.js:

1. Minimalistic features: While the simplicity of Express.js is one of its strengths, it can also be a limitation for some use cases that require more advanced features out of the box. In such cases, developers may need to extend Express.js with additional middleware or plugins.
2. Lack of strict architecture: Express.js is a lightweight framework that doesn’t enforce any strict architecture or conventions, which can lead to inconsistency and complexity in larger applications.
3. Asynchronous nature: Although the non-blocking I/O API of Node.js allows for high concurrency and scalability, it can also lead to callbacks, promises, and async/await complexities in Express.js.
4. Steep learning curve: While the API of Express.js is relatively simple and intuitive, it can still have a steep learning curve for developers who are not familiar with Node.js or server-side development.
5. Security risks: While Express.js provides some built-in security features, developers must still take additional measures to ensure their applications are secure, as Express.js is susceptible to common web application security risks such as SQL injection and cross-site scripting (XSS).

Companies using Express JS

Express.js is a popular web application framework for Node.js and is used by many companies worldwide. Here are some of the well-known companies that use Express.js:

1. IBM – IBM uses Express.js as part of its cloud platform, IBM Cloud.
2. Uber – Uber’s internal engineering team uses Express.js to build the company’s web applications and APIs.
3. Accenture – Accenture uses Express.js as part of its development stack to build web applications and APIs.
4. PayPal – PayPal uses Express.js to build its web applications and APIs.
5. LinkedIn – LinkedIn uses Express.js as part of its development stack for building web applications.
6. Mozilla – Mozilla uses Express.js for building its open-source web applications and APIs.
7. Trello – Trello, a popular web-based project management application, uses Express.js as its backend framework.
8. GoDaddy – GoDaddy uses Express.js for building its web applications and APIs.
9. NPM – NPM, the world’s largest package repository for Node.js, uses Express.js for its web applications and APIs.

Installing Express JS and Creating First Program

Install Node.js: Express.js is built on top of Node.js, so you’ll need to have Node.js installed on your system. You can download and install the latest version of Node.js from the official website: https://nodejs.org/en/download/

Create a new project directory: Open your terminal or command prompt and create a new directory for your project. You can do this by running the following command:

mkdir my-express-app

Change directory into your project: Navigate to your project directory by running the following command:

cd my-express-app

Initialize a new Node.js project: Initialize a new Node.js project in your project directory by running the following command:

npm init -y

This will create a new package.json file in your project directory.

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

npm install express

Create a new file: Create a new file called index.js in your project directory. You can do this by running the following command:

touch index.js

Open index.js in your text editor and add the following code:

const express = require('express')
const app = express()

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

app.listen(3000, () => {
  console.log('Server listening on port 3000')
})

This code sets up a basic Express.js application that listens on port 3000 and sends a “Hello World!” response when you navigate to the root URL.

Start the server: Start the server by running the following command in your project directory:

node index.js

Test the application: Open your web browser and navigate to http://localhost:3000. You should see the message “Hello World!” displayed in your browser.

That’s it! You’ve successfully installed Express.js and created your first Express.js application.

Written by: Piyush Patil

I hope this guide has helped you understand what Express.js is, its features, advantages, limitations, and how to install it and create your first program. Express.js is a powerful and flexible framework for building web applications and APIs with Node.js. Its simplicity, flexibility, and large ecosystem of plugins and middleware modules make it a popular choice for developers. If you’re interested in building web applications and APIs with Node.js, I encourage you to continue exploring Express.js and its capabilities. Happy coding!