by Alexandre Levacher

How To Organize Express Controllers For Large Codebases

Three years ago, I started developing an Express.js API for a company. I wondered what could be the best controllers architecture to stay organized as the codebase grows.

Influenced by Sails or Rails and by my research, I came to create my own system. I did not want to overload my project using a complete framework like Sails, but rather pick lighter dependencies when needed.

So I created an organization system for the app’s controllers which I paired with a homemade loader. Since then, I improved both of them thanks to the experience I gained by implementing it on other projects.

Today, I’m confident enough with this method to share it, as the results are convincing.

From what I know, it’s used by a few large companies. It simplifies onboarding new developers as it makes the codebase easier to read.

✅ Here’s how to set up a clean controllers architecture.

The Structure

If you don’t anticipate the growth of your app, you’ll quickly have an unorganized codebase. I designed the organization method to have wide compatibility, which means that someday you’ll not be locked into a kind of use case you can’t solve with this method.

Setup your file tree

  • Group routes in controllers
  • Create folders for each controller
  • Create a routing file in each controller which describes the path of each route, the method to call, its optionally associated middleware, and the restriction level.
  • Create a file for each controller's actions which contains the method to execute and the middlewares.
  • Create a spec file for testing

Let’s see how it looks.

🗂 Example of controllers structure

Don’t be afraid to create a lot of files. It does not slow down the development, and it makes your codebase neat and airy. ✨

Load your routes

To make things work following the structure defined above, we need to use a simple loader I created: Lumie. It will go through your controllers, read the definition files, and load your routes.

It’s a small package, you can check to code source on GitHub.

Routing Files

They have been designed to be easy to read. The purpose is to be able to identify methods to update in development by having a quick look in your .routing files. In the following example, three routes will be created:

  • [ PUT ] /user
  • [ GET ] /user
  • [ GET ] /user/reset-password

You are wondering why routes are prefixed with “user” although it’s not described in the routing definition. Lumie uses the name of the folder in which the routing file is to prefix routes.

Here, we are in controllers/user/user.routing.js . If the user folder has been in a subfolder admin for example, the routes would have been prefixed by admin/user.

Note that you can pass an optional path field to the routing definition so it will be used instead of the default one.

Actions & Middlewares

As you can see above, each routes configuration have an action method which is nothing more than the logic to execute when we call your API route. I recommend keeping in one file: one action method and its optional associated middleware.

Restrictions

For each routes configuration, you’ll choose the restriction level associated. The level value will be passed to the restriction function you’ll create to make Lumie work. See how to initialize Lumie with your own restriction function.

This should be just a function that returns a classic express middleware.

Conclusion

I’ve been using this method for a while now. I like to have this kind of opinionated framework to follow when I develop. At the end of the day, it’s helping me to keep a nice codebase and not to take shortcuts like writing too much logic in one file or defining a route in an inappropriate file.

Thanks for reading. Tell me in the comments what you think about organizing controllers this way.

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