Introduction to Express.js

Express.js is a back-end development node framework for developing web applications. It is notable for providing strong set of features with support for both mobile and web applications. It’s flexible and minimal development style is what attracts the developers most. Express is also a part of the MEAN stack development along with Angular being the front-end and MongoDB providing the database support.

Express.js development style

One of the best things about Express is that it provides API for building web applications therefore you don’t need to work on low level processes and protocols. A number of modules are available on npm which can you can directly include in your working environment.

Integration using Pug

Pug, a terse language for HTML templates, is used to easily integrate Express.js into your environment. It can:

– Produce HTML
– Provide dynamic code support
– Provide re-usability support

To provide better overall experience to the user, Express modifies most of the defaults after Pug’s integration.

Main Features of Express.js

Express.js makes it a lot easier for to communicate with Node.js. Reason for choosing it over Vanilla is that Vanilla has less features and that it’s options are limited. There are four main features in Express.js.

  • Middle-ware: In Node.js, a request handler function works in a way that it listens to your function and sends response out of the function. Here to minimize this process, Express has these smaller request handler functions called Middle-ware functions and you can call several of them.
  • Routing: The request handlers (Middle-ware functions) are executed conditionally, It depends on the type of HTTP method and URL which the client sends.
  • Sub-applications: Express.js applications are so small that you can easily fit them into a file. But even if the applications gets larger, Express has a solutions for this too. Sub-applications is such feature which can help you scale your app. This is basically done using the routers.
  • Conveniences: Express creates easiness in many ways. Building applications in express is all about routing and middle-ware functions. Now in simple Node.js, this can get pretty messy but in express, you need to just call in one method. Like in Node.js you can multiple request handler functions to send a JPEG image but in express you just call sendFile method.


ExpressJS’s stable release v.4.16.1 is available under MIT Licence at their github repository.