Express.js is a popular web application framework for Node.js that simplifies the process of building scalable and robust server-side applications. With its minimalist design, middleware support, and routing capabilities, Express.js has become a go-to choice for developers looking to quickly create APIs and web applications.
What is Express.js?
Express.js is an unopinionated, lightweight, and minimal Node.js backend framework that provides tools and features for building web apps, APIs, and hybrid/cross-platform apps quickly and more efficiently. Express.js is open source and free to use, it’s written in JavaScript, and is hosted within the Node.js runtime environment.
Express.js has access to a vast collection of JavaScript libraries and modules, contributed by a large and active community. Express.js is used as the backend part of the MEAN and NERD full-stack JavaScript stack to manage routing, sessions, HTTP requests, error handling, etc. Specifically, in these areas, Express.js enhances the functionality of Node.js by saving on time spent coding and streamlining efficiency. Here are some of the key properties of Express.js:
With over 58k GitHub stars, Express is arguably the most popular Node.js framework, boasting a large and active community. Developers can access large JavaScript libraries to help them build more efficient apps and reduce the time spent writing repetitive code. Technically speaking, Express.js is a Node.js module that uses middleware to expand its functionality through custom code or code that’s been contributed by the community.
Is Express.js a framework?
Express.js is the most popular Node.js back-end framework. It’s built on top of Node.js’s built-in HTTP module and is made to help with routing, handling the request/response cycle, error handling, sessions, and more. Express.js is a lightweight, minimal, fast, and unopinionated Node.js framework, which has led to it being adopted by dozens of large and well-known companies. Express.js is also the underlying library on which several Node.js frameworks are built, including NestJS, Kraken, and KeystoneJS.
How Express.js works
Express.js is a standard choice for building back-end web servers with its powerful routing system, and ability to easily add functionality to a back-end server via extensive middleware and templating engines for building dynamic web pages. Many Express.js applications are built to be cloud-native or are hosted in the cloud.
When a user enters a website address into their web browser, an HTTP request is sent to the CDN, which in turn responds with HTML, CSS, and JavaScript to the browser. The browser executes the JavaScript, instructing it on how to fetch the required data through JavaScript hydration.
Subsequently, the browser sends a request to the backend server, specifically the Express server, where the server receives the request via one of its routes. The server then processes the request using the corresponding controller for the route. Once the request is handled, the server sends back an HTTP response to the client.
Express.js uses a client-server model to process and handle a client’s request and return a response back to it – much like many other popular frameworks such as Laravel.
Why use Express.js?
Express.js is a lightweight, fast, and flexible backend framework that provides functionality to make Node.js easier and more efficient in use cases including building single page applications (SPAs), middleware applications, RestFUL APIs, accessing and serving static files, etc.
According to a study by SimilarTech, Express.js is used in over 230,000 websites. Another study by BuildWith shows that Express.js is the 9th most popular framework used by the top 10,000 sites, ahead of both Angular and Next.js.
Building scalable applications
Express.js has a speedy I/O, allowing it to respond quickly to user requests, along with its efficient request/response cycle. An MVC (Model – View – Controller) architecture enhances data manipulation and helps keep the codebase organized and maintainable, which can be important concerns for building scalable applications.
The MEAN stack
The MEAN technological stack is a popular full-stack web development framework that combines four key components: MongoDB (a NoSQL database), Express.js (a web application framework), Angular (a frontend framework), and Node.js (a runtime environment). MEAN helps developers build dynamic and scalable web applications using JavaScript throughout the entire development process.
Fast, flexible, and extensible
Express.js provides a robust feature set and is easy to get started with, despite being a very lightweight and flexible framework. Through extensive features for building middleware, routing, and templating, Express.js offer speedy development. Much of Express’s flexibility comes from being unopinionated – meaning that you aren’t forced into specific styles and set rules for writing code and building applications.
“Express.js provides a robust feature set and is easy to get started with, despite being a very lightweight and flexible framework.”
Extensibility is another strength of Express.js; whereby third-party modules and libraries offer powerful ways to extend Express’s capabilities and functionality. These libraries are constantly growing and evolving thanks to a large, dynamic, and active Express community.
Large and active community
As the largest Node.js framework, Express.js has a large and active community contributing a variety of extensions, middleware modules, libraries, and more. Express.js is open-sourced, meaning developers can extend its functionality using existing modules and libraries, and use reference in-depth guides on routing, middleware, best practices, etc.
Features of Express.js
Express.js is not a magic cure-all solution when building web applications. As it’s hosted within the Node.js runtime environment, Express.js benefits from Node’s strengths. Here we explore key features to better understand where Express shines and what makes it unique:
Quick server-side development
Express.js provides robust features and functions that significantly accelerate server-side development compared to using just Node.js. It offers a wide range of pre-built modules and libraries, reducing the time and effort required to write code from scratch.
Routing
Express.js provides powerful routing features, allowing developers to define how the server application responds to user requests to specific endpoints. Express’s flexible routing capabilities work seamlessly with its extensive middleware, enabling efficient request handling and response management.
Middleware
Express.js offers a rich collection of middleware components, making it easy to incorporate additional functionality into the server application. Middleware functions in Express handle and process user requests after they are received by the server, but before the controller’s action sends the response. This modular approach simplifies request handling and promotes code reusability.
“Express.js offers a rich collection of middleware components, making it easy to incorporate additional functionality into the server application.”
Debugging
Express.js includes an internal debugging module that facilitates efficient debugging of applications. It logs detailed information about middleware usage, route matching, application mode, and more. This valuable data aids developers in pinpointing bugs and resolving issues promptly, enhancing the overall development and debugging experience.
Templating
Express.js integrates with templating engines, such as Pug, EJS, and Mustache. Templating engines let developers use static template files within their applications, where template variables are replaced with actual data at runtime, generating dynamic HTML files to be sent to the client. Express’s templating support simplifies the creation of dynamic web pages and streamlines the process of rendering dynamic content.
Authentication
Express.js provides built-in support for implementing authentication in web applications. It offers various middleware and strategies for handling user authentication, such as passport.js integration, session management, and authentication middleware functions. This feature helps developers easily secure their applications and manage user access based on authentication credentials.
Benefits of using Express.js
When harnessed effectively, Express.js offers a powerful and efficient way to build scalable, performant, and flexible applications. It can save a lot of development time and resources, reduce boilerplate code, and ensure developers can focus on functionality and business logic. Let’s take a look at some of the most common benefits of using Express.js.
Unopinionated
Express.js is unopinionated, meaning it doesn’t force you to adopt specific coding practices and rules. Applications can be flexibly built from the ground up.
Scalability and performance
Express.js provides a lightweight and minimalistic framework that gives developers fine-grained control over their application’s performance and scalability.
Easy to learn
Express.js is the most widely used Node.js framework and has an active community that provides guides, established best practices, modules, libraries and utilities.
Fast to link with databases
Express.js integrates quickly and easily with databases such as MySQL, MongoDB, PostgreSQL, etc., by simply loading the required Node.js driver to your Express app.
Fast app development
Express plays a key backend role in the MEAN stack and can build entire applications using only JavaScript, saving time and streamlining code maintenance.
Supports 3rd party plugins
Express.js supports a wide range of third-party plugins and modules that can be used to extend its capabilities and functionality beyond what’s available out of the box.
Drawbacks of using Express.js
Here are some of the common issues with using Express.js. Bear in mind that much of Express.js effectiveness comes down to the project team, familiarity with Express’s preferred design patterns, etc. The below disadvantages are also situational, depending on where and how Express is used and the size of the project or application.
Lack of structure
Express.js’ unopinionated nature can be a drawback. The lack of strict or guiding universal ways to structure code/folders and application can be tricky, leading to messy code and potentially slower rest APIs.
Complex error messages
Error messages in Express.js aren’t always helpful and can be quite complex. While this isn’t always an issue, it can become troublesome when debugging large or complex applications.
Lightweight
While being lightweight and minimal is often put forward as benefits, they can also be disadvantageous. Express.js is lightweight out-of-the-box, often requiring a lot of boilerplate code.
