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In this tutorial, you will learn what is express js, what is its use, its features, architecture, versions and companies using it with example. So let’s start with Express JS Introduction.
What is Express JS?
Express.js is a web application framework for Node.js, designed for building robust, scalable, and efficient web applications. It simplifies the process of creating dynamic and interactive web pages, as well as APIs (Application Programming Interfaces).
Express.js is built on top of Node.js and provides a minimalist framework for creating web applications. It is designed to be flexible, allowing developers to build applications the way they see fit.
Features of Express.js:
1. Routing:
ExpressJS provides a simple and flexible routing system that allows you to define URL paths and HTTP methods to handle incoming requests. This allows you to build complex web applications with ease and helps you maintain clean and organized code.
2. Middleware:
ExpressJS middleware is a powerful feature that allows you to add additional functionality to your web application’s request and response handling pipeline. This can include features such as authentication, logging, compression, and more. ExpressJS provides a range of built-in middleware functions, as well as the ability to define your own custom middleware.
3. Templating engines:
ExpressJS supports a variety of templating engines, including Pug, Handlebars, and EJS. These engines allow you to easily generate dynamic HTML pages and provide a range of features, such as conditional statements and loops, to make your templates more powerful and flexible.
4. Error handling:
ExpressJS provides a robust error handling system that allows you to handle errors and exceptions in a consistent and organized manner. This includes the ability to define custom error handlers, as well as the ability to handle errors at different levels of the application stack.
Express JS History
Version 1.x
The first version of Express.js was released in 2010 and had limited functionality. It provided basic routing and middleware capabilities, but did not include support for templates or other advanced features. Version 1.x is no longer maintained and is not recommended for use in production.
Version 2.x
Released in 2011, Express.js 2.x introduced several new features, including view engines, middleware stacks, and support for multiple routes per file. This version also included a number of bug fixes and performance improvements.
Version 3.x
Express.js 3.x was released in 2012 and included significant changes to the routing and middleware architecture. This version also included a new routing syntax and introduced support for a wider range of view engines.
Version 4.x
Express.js 4.x is the current stable version of the framework and was released in 2014. It includes several new features and improvements over previous versions, including better middleware support and improved error handling. Version 4.x also introduced a new Router object for modularizing routes, allowing developers to separate different parts of an application into smaller, more manageable modules. The latest release of Express.js 4.x is version 4.18.2, which was released in 2022.
Version 5.x
Express.js 5.x is currently in development and is expected to be released soon. This version includes several new features and improvements, including better support for HTTP/2, improved performance, and a simplified API. This change is intended to make it easier for developers to build modular applications and reuse code.
Architecture of Express.js
Express.js is built on top of Node.js and follows a middleware-based architecture. Middleware functions are functions that have access to the request and response objects and can modify them or perform additional actions before passing control to the next middleware function.
Express.js applications are built by defining routes, which map URLs to middleware functions. When a request is made to a URL, the middleware functions associated with that URL are executed in order. Each middleware function has the ability to modify the request and response objects, and can also pass control to the next middleware function in the chain.
The modular architecture of Express.js makes it easy to add or remove functionality from an application. Developers can create their own middleware functions or use existing middleware functions provided by the community.
Nees of Express.js
1. Speed and performance: Because Express.js is built on top of Node.js, it is designed to be fast and efficient, making it ideal for building high-performance web applications.
2. Flexibility: Express.js is designed to be flexible and un-opinionated, allowing developers to build applications the way they see fit.
3. Large community: Express.js has a large and active community of developers, which means that there is a lot of support and resources available.
4. Easy to learn: Express.js has a relatively small learning curve compared to other web application frameworks, making it a great choice for developers who are new to Node.js and web development.
Express.js is built on top of Node.js, which is a server-side JavaScript runtime environment. It provides a simple yet powerful API that makes it easy for developers to create web applications that can handle various HTTP requests and responses, including handling requests for static files, handling routes, and working with middleware.
Prerequisites to learn Express JS
1. JavaScript: Express.js is a framework built on top of Node.js, so you should have a good understanding of JavaScript concepts such as variables, functions, arrays, objects, and control flow.
2. Node.js: Express.js is built on top of Node.js, so you should have some familiarity with Node.js and its core modules.
3. HTTP: You should have a basic understanding of the HTTP protocol and how it works. This includes knowledge of HTTP methods (GET, POST, PUT, DELETE, etc.), status codes (200 OK, 404 Not Found, etc.), and headers (Content-Type, Accept, etc.).
4. Middleware: Express.js heavily relies on middleware functions to handle requests and responses, so you should understand what middleware is and how it works.
Having this prerequisite knowledge will make it easier for you to understand and work with Express.js. However, don’t worry if you don’t have experience with all of these concepts. You can still learn Express.js by following tutorials and reading documentation.
Everything about Nodejs before starting Expressjs
Before starting with Express.js, it’s important to have a good understanding of Node.js, as Express.js is built on top of Node.js. Here are some key concepts and features of Node.js that you should be familiar with:
Asynchronous programming: Node.js is designed to handle a large number of simultaneous connections efficiently by using an event-driven, non-blocking I/O model. This means that Node.js applications are typically written using asynchronous programming techniques such as callbacks, Promises, and async/await.
Node.js modules: Node.js provides a modular architecture, where each module is a standalone piece of code that can be reused in other applications. You should understand how to create and use modules in Node.js, and how to install and use third-party modules using tools such as npm.
CommonJS modules: Node.js uses the CommonJS module specification for defining and importing modules. You should be familiar with the syntax for defining and exporting modules using module.exports and exports.
The Node.js runtime: You should understand the basics of how the Node.js runtime works. This includes event loop, single-threaded architecture, and ability to use multiple worker threads for CPU-bound tasks.
Error handling and debugging: You should be familiar with techniques for error handling and debugging in Node.js. This includes the use of try/catch blocks, error events, and debugging tools such as the Node.js debugger and the Chrome DevTools.
Having a good understanding of these concepts and features of Node.js will make it easier for you to learn and work with Express.js.
How to create a basic Express.js application:
const express = require('express')
const app = express()
app.get('/', function (req, res) {
res.send('Hello, from DataFlair!')
})
app.listen(3000, function () {
console.log('Example app listening on port 3000!')
})
Output:
The given code demonstrates a basic example of creating an Express.js application. It starts by importing the Express.js library and creating an instance of an Express.js application using express(). Then, a route is defined that responds to GET requests to the root path (/) with a simple string message using res.send(). Finally, the application is started and set to listen for incoming requests on port 3000 using app.listen().
When the application starts up, a message is logged to the console indicating that the server is listening. This is a simple example of how Express.js can be used to create a web server and handle incoming requests. The framework provides a variety of tools for building more complex applications making it a popular choice for web developers.
Companies Using Express.js
Express.js is a widely adopted web framework and is used by many companies, both large and small, across various industries. Some notable companies that use Express.js include:
Uber: Uber uses Express.js to power its web application and APIs, enabling it to handle millions of requests per day.
IBM: IBM uses Express.js to build cloud-native applications and APIs.
PayPal: PayPal uses Express.js to build scalable and secure web applications and APIs.
Accenture: Accenture uses Express.js to build enterprise-level applications that can handle complex business logic.
Netflix: Netflix uses Express.js to power its streaming services and APIs, enabling it to deliver high-quality content to millions of users.
Conclusion:
Express.js is a powerful and flexible web application framework that can help you build high-performance web applications quickly and easily. With its simple and intuitive API, it is an ideal choice for building modern web applications.