crafting (and) JavaScript

NodeJS Architecture Applied

The article Node.js, Dependency Injection, Layered Architecture, and TDD: A Practical Example, Part 1 by @Carlos González gives a very good introduction of how to structure a (TypeScript/JavaScript) app. He links articles that allow one to dive deeper into underlying concepts and still explains the big picture very well. Great job Carlos!

He starts by explaining The "D" in SOLID (Dependency Inversion) which might feel a bit clunky if you haven't heard of it before. But I have to say at this point, stick to it, the benefit will become obvious while working with a code base as he is creating it and especially testing will be so much more beneficial. While the "D" (driven) in TDD will also push you that direction anyways.

Next he writes about Layered Architecture explains it very quickly and easy to understand, applicable right away. He dives into many more very important topics. Just go and read the article, it is great!

I just want to dive deeper into two things.

More TDD, Please (1)

I just strongly miss the TDD part. If you know me, you knew I was going to say that. Parts in the article describing how to do things, without diving into "why" makes the purpose of architecting a bit too much a self-purpose, though this is what the article is mainly about. Still, I believe that using the "driving" through tests might also very well supports some architecture decisions and can help explaining them better.

Reading some tests like in todo.service.spec.ts feels a bit too much like testing the "how" instead of the "why" and "what". This might lead people into the wrong direction, that's why I think it is important to make sure not to learn testing this way. Reading a test description such as 'assignTo should internally call findOneOrFail instead of findOne' already states that it describe implementation details. There are low-level tests that sometimes look like this, I agree. But these sometimes feel like they are testing the mikro-orm and I believe that should not be the intention.
The article Learning By Testing by @Raimo Radczewski has a lot of good hints on this topic.

Reading further Carlos states that about some TDD things that

We will discuss that further in part 2 of this series.

Really cool!

Don't get me wrong, I like the trade-offs he makes and the focus, still deep knowledge he has put into this article. I am looking forward to part 2, because

in part 2 of this series we will focus a little on Test-Driven Development but especially how we can set up Integration Testing using Docker for our project.

Especially the docker part I am really curious about. I have also talked about TDD your next docker container last year, the code in is this repo on codeberg (codeberg = github + independent).

Too Many new Terms? (2)

When I started reading this article, I started out to be a bit opposed to the idea of using so much tooling, like nestjs, an ORM, TypeScript, etc. But I have to say in the context of learning architecture those tools might be a great base to build on to practice those principles and to be productive faster. Learnings about the architecture layers and practice software architecture without bothering too much about the underlying structures and technologies might be a benefit to grasp the concepts quickly.

Learn What is Below Architecture!

If the described software architecture and things like NestJS that uses Express.js under the hood (sic), ORMs, TypeScript, TDD, SOLID or any of those are new to you, if phrases like

Dependency Injection is a bit different in TypeScript [...] dependency abstractions are done with interfaces and it is with those same interfaces that you register a provider in an IoC container


TypeScript compiles down to JavaScript and when this happens interface and type information is lost


TypeScript offers [...] abstract classes


mikro-orm already provides repositories for our entities

are hard to understand or sounds like magic I strongly recommend to take the time to learn architecture in a more profound way, than the article suggests. I suggest remove all the layers of software, like the ORM, TypeScript, nestjs, etc. Start practicing the core techniques and technologies, some of them are:

  • JavaScript (the language), including npm
  • TDD
  • Design Patterns.

Even this list is already very long and it took me years until I was able to understand how and when to reach out for them. Let alone TDD, I believe after I had a crash course from JB Rainsberger it took me two years to start being confident to apply it and make software, I wrote, benefit from it. During those two years I basically just made mistakes. Anyways, it is worth to start chopping up the learnings into smaller and more widely applicable learnings.

Fight Software Bloat

Why am I saying that? I have seen it too often that the levels of abstraction that we take for granted are actually not so abstract as one thinks, they are often very much simpler than one imagines. Starting to learn on top of those abstractions leads to a missing understanding of the underlying principles and technologies, which will lead to inefficiently applying them and result in the bloated software, which seems to be mainstream nowadays (in JavaScript land).

An example makes this easier to understand. I remember learning about test libraries (such as mocha, jasmine or jest) with a mentee a couple years ago and I learned that he saw them as a given and "magic that I will never understand". Once we took apart what a test library does and he had implemented one himself he was ready to unleash the covers and realize that there is no magic at all. One just has to lift the covers. But doing that requires the push into that direction.

Less is More

That is the push I wanted to give as a second take away from the article. Unleash the covers of the layers below and you will be surprised how many layers deep it goes. You will see, with much less you can achieve the same.

If this sounds reasonable and you have questions feel free to reach out to me on twitter.