Letter Casing in Names of Imported NodeJS Modules

Disclaimer: This isn’t a tutorial, guide, or holy writ. This is just how I do things and I’d like to share why it makes sense to me. If it resonates with you, follow it. If it doesn’t, follow whatever makes sense to you and your team.

Styleguides are something I take very seriously. To me a programmer who has great style and writes clean, readable code is worth a lot more than someone who’s just clever with algorithms. Cleaner code results in better collaboration within teams and better maintenance of the project going forward.

Now one of the things every good styleguide has is a sensible naming convention. This can mean both conventions for variables and functions on a very broad level, as well as a subtler level- things such as the letter casing of imported modules.

Yes, I wrote an entire post about how I case the names of my modules.

I follow a very specific naming convention for when I import modules in NodeJS. Though they differ for on-site modules and vendor modules, for each, the rules are [mostly] consistent.

Here’s what I do and why I do it.

Project Modules

These are the modules you write as part of your own project. I won’t go into how you should structure your source files or name them: that’s beyond the scope of this article. But let’s talk about how you can name them once imported into another module.

Previously, I used to be of the name everything in camelCase camp. I literally used to name everything in camelCase without any thought to context or suitability. Why? Because everyone else did it, so why not?

After I joined the company I’m working at as of this writing, I was introduced to a new styleguide, one of the rules of which was: Use uppercase variable names for imported modules. I went along with it coz I did not see a reason not to. It’s actually one of the conventions picked up from the Hapi styleguide.

Now the Hapi styleguide honestly sucks. Not because any of the conventions are wrong: I’m not sure if conventions, by their very definition, can be wrong (correct me if I’m wrong on this point). Conventions are conventions. They just are.

I’m thinking of writing a whole other post to talk about why I dislike Hapi’s styleguide.

After thinking about it for a while I realized how PascalCased names can be advantageous in certain situations.

In Java, with its concept of classes and interfaces, a class or interface would be PascalCased to indicate that it’s not an instance but a class. Its functions would be static i.e. without an object context. Instantiated objects would be camelCased and have non-static methods.

Javascript, though object-oriented, does not have classes or interfaces; its inheritance is based on prototypes. Moreover the object in Javascript can also be used (and is extensively used) as what would be a dictionary type in other languages.

Now, what’s the advantage of naming modules required from within your own project in PascalCase? You can immediately differentiate between those that are instances vs. those that are just plain objects.

Consider a module imported like this:

const MyModule = require('path/to/my_module')

Most likely it will be composed of functions that should be used as-is, without a this context attached to them. Those functions are just functions and not methods i.e. they don’t have an object they are bound to. You can freely pass these around without any issues.

On the other hand, when you have a module that exposes an object instantiated from a class (I know I said Javascript doesn’t have classes, and it doesn’t; read this for clarity), or a constructor function, you expose it as such.

So say I have an instance of an AWS Lambda service. I’d expose it as so:

const AWS = require('aws-sdk');
const lambda = new AWS.Lambda({apiVersion: '2015-03-31'});

module.exports = lambda;

And I import it:

const lambda = require('path/to/lambda.js')

Vendors like AWS also use this convention where a module which has functions that are free of a this context are in PascalCase to indicate that they are class like, while the instantiated object itself is in camelCase.

It’s a subtle difference and it’s not necessarily the best convention (if you find the best one, do let me know), but it makes sense and it works for me.

To summarize:

  • If I’m exposing a module with functions not bound to any objects, I think of that module like you would a class in Java where all the functions are static ones. These are always PascalCased.
  • If I’m exposing a module which is already instantiated- hence its methods are bound to the object- I think of these like instantiated objects in Java. These are camelCased.

It’s that simple, really.

Vendor Modules

These are the third-party libraries you get from the npm registry (pretty-much 99% of the time), or directly via a github remote url.

My policy with vendor modules is this: I try to name them the same way the vendors themselves have in their example code on github npm website blog.

Why?

To make things more readable.

How does following the vendor’s own convention for their library’s usage help in code readability?

Here’s how:

  • Using libraries the way that the owner/maintainer uses it means that when someone looks at your code and looks at the vendor’s examples, they’ll be seeing the same thing. They can map those examples to your code much faster.

  • Since the usage is what’s shown on the library owner’s GitHub/Npm page, that’s most likely how other people have used it too. Stackoverflow posts, tutorials, blog posts, examples, what-will-you; reading other people’s code/blogs about the library becomes easier if you see a library being used in the same way.

This seems like a small thing, but when you’re reading code a certain number of weeks down the line, or debugging stuff by googling it, having vendor libraries named in the same way everywhere really helps.

There are exceptions to every rule, of course, and one of mine is the coroutine function from Bluebird.

I always import it as:

const co = require('bluebird').coroutine;

Why?

  • I make use of the coroutine pattern extensively (at least once in every asynchronous function) in my code and writing co instead of Promise.coroutine simplifies life.

  • Using co this way is not something I came up with on my own. TJ Holowaychuk’s co library has the same pattern. I use Bluebird’s implementation because it’s faster (sorry TJ 😅) but TJ’s code is familiar enough that I think others (and myself) will understand what the intent of the function is.

In Conclusion…

…I love having a set of rules defining code style. It helps me read code faster, helps me grok it faster, and makes me more productive. But even the most stringent rules have to be broken at times and that’s what it really comes down to in code craftsmanship: knowing when to follow the rules and when to break them.

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