A Deep Dive on MERN: Introduction to Express.js


This is article 4 of 4 exploring each technology in the MERN stack:

To check out our overview of the stack and why it is so popular, you can see our article here. In these articles, we’ll go a bit deeper on each technology, their history, and even tease out what the future of each will hold.

Without further ado – here’s Express.js!

Understanding the Role of a Middleware in Web Development

Continuing the coffee shop metaphor, imagine visiting a coffee shop where the barista not only serves you coffee but also offers personalized recommendations, can quickly modify the menu items to fit your custom order, and ensures that your coffee reaches you with the exact blend and specifications you asked for, every time. This barista’s role is similar to what Express.js does in the world of web development. In this analogy, if the coffee shop is your web application, Express.js is the skilled barista who streamlines the process between the customer ordering (sending a web request) and enjoying their coffee (receiving the web response).

What is Express.js?

In the digital world, Express.js is a web application framework that simplifies the process of building server-side applications by offering a suite of tools and features for handling web requests and responses. It’s important to remember that the core requirements of web applications tend to be very consistent across different projects. That means that there is often already an established solution or “best practice” on how to implement a feature in an application. Frameworks like Express.js encapsulate these best practices, offering developers pre-constructed modules and libraries that address common tasks. Utilizing a framework like Express means that developers can bypass a lot of the busy work of getting an application off the ground and focus on the more customized functionality they need for their own purposes.

The Emergence of Express.js

Developed in 2010, Express.js quickly became a big part of the Node.js ecosystem. It was designed to tackle the complexities of server-side development by providing a more intuitive and flexible way to create web servers and APIs. This made it easier for developers to build reliable web applications without having to start from scratch. Imagine how much easier it would be to open a new coffee shop if you hired experienced baristas who already knew how to do the job and give customers a great experience. The baristas come in on day one, already well-versed in the requirements of the job. Express does the same thing for web developers! When you start a new application with Express, you’re working with tried and tested tools that were designed specifically to speed up the development process.

Why Express.js is Widely Used

Express.js gained popularity for a number of reasons:

  • Simplicity: Just as a barista might use a simplified brewing system to quickly and consistently produce high-quality coffee, Express.js offers a straightforward approach to web development, making it accessible even to those new to the field.
  • Flexibility: Express.js, like a skilled barista, can adapt to a wide range of customer requests, from simple black coffee to complex, custom-blended beverages. This flexibility allows developers to build a variety of web applications, from single-page applications to complex RESTful APIs.
  • Efficiency: With Express.js, handling an order—from taking it to serving the coffee—is streamlined, reducing wait times and improving customer satisfaction. Similarly, Express.js optimizes the processing of web requests, making web applications faster and more responsive.

Are there downsides?

  • Flexibility: Express.js is known for its flexibility, but this can also be a double-edged sword. The minimalistic and unopinionated nature of Express means developers have to make more decisions about the architecture and tools they use, which can lead to decision fatigue and inconsistencies across different projects.
  • Lack of Conventions: Unlike more opinionated frameworks that prescribe a specific way to organize and develop applications, Express.js leaves much of the structure and organization up to the developer. This can lead to varied approaches within teams or projects, potentially making codebases harder to understand and maintain.
  • Dependency on Middleware: Many features that are essential for web applications, such as body parsing, session management, and security features, are not built into Express.js itself but are instead added through middleware. Managing these middleware dependencies can become cumbersome, especially as the application grows.


Express.js has established itself as an indispensable tool in the world of web development. Its simplicity, flexibility, and efficiency make it a go-to framework for developers aiming to build robust, scalable web applications in JavaScript. As the digital landscape continues to evolve, the role of Express.js in shaping the future of web development.

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