What were some of the toughest technologies and concepts for you to grasp along the way?

I'll go first with a few:

• Git: It took me a while to learn the basics, and it's still something I don't feel like an advanced user of. I tend to stick to the commands I'm most comfortable with.
• Testing: This took a while for me to get the hang of, but I feel like it's turned into a strength. I love TDD and find great comfort in a well-written regression test. 😅
• Typed languages: I think I got into the domains of untyped languages as a career because I had some mental blocks around types. These days I'm much more comfortable in either domain, but happen to still work mostly with Ruby, my fave lang.

I used to always hate CSS. I just couldn't understand any of it. I said I want nothing to do with it and stayed learning backend development with C# and ASP.NET. Fast forward a couple years and now I'm labeling myself as a Front-End Developer. Ive always loved making things look good but css just didn't click with me for a while. Not sure what changed but suddenly I understand a good amount of it. Still haven't touched grid but hey flex is working just fine so far.

It's funny, but it took me the longest time to grasp the concept of a function parameter. I didn't understand what they were or how they altered what the function would output.

I finally got it when I found this simple example in JS that illustrated it well.

function feetToInches(feet) {
   return feet * 12;
}

I feel so dumb now, but I guess it kind of illustrates how far I've come! 😃

I still find async tricky. I was puttering along fine using Rust's flavor of it until I needed to use tokio::select! - even though I understand it now and can use it effectively in solutions, the code is just not intuitive for me. It takes me a while to think through, and often some napkin-scribbling.

Docker

For me its Regex, I still don't get it right.

I will say testing things properly is the biggest one.
And also probably the biggest step from programmeur amateur to becoming a professional.
I haven't figured out testing fully to be honest, but I'm definitely better than I used to be.

Ugh, I was really dumb back then. In my first month as a programmer:

• What the world does return mean?? What is it supposed to do?
• Why do I have to create a class just to access a method (I started out with Java)? Does OOP stand for obscene obscure programming?
  • What's OOP and why use it??

After a while in web dev, I had a hard time understanding:

• Why every time I access the DOM it just says [object Object]? lol
• CSS:
  • It's really frustrating because I didn't know how properties work with each other, and thus the CSS "didn't do anything"

Later as a fullstack dev:

• NodeJS was confusing to learn

Later learning JS frameworks:

• Cannot use import outside a module ... invalid module path
  • What in the world is webpack? Why use babel?

After learning about security and authentication:

• How in the world do I keep hackers out??

Learning Rust:

• Ownership is sooooo annoying and confusing

In my career now as a ML dev:

• What's a neural network?
• How does ML even work??

I'm glad to be over all that now, although I'm sure something new will come up sooner or later. I guess it makes me understand those people on SO who have literally no idea what they're doing, because many years ago I was one of them.

Starting out, the concept of "frameworks" and "libraries" confused me a lot. Not just the distinction between the two, but how they actually work, and the patterns they guide you into. For example, when I first heard about them, Jquery and Angular looked completely foreign to vanilla JS. They might as well have been separate languages to me.

Regex was a complete mystery to me for years. It still sort of is, but I can at least parse it mentally and create some basic ones. I still have to use regexr.com/ to test them though, lol

Linux was pretty tricky to learn. I was pretty much obligated to learn it because I was managing a php server. Docker actually made this process a lot easier. It's not the shell that gave me trouble, rather it was the nagging feeling that I wasn't fully understanding something, not getting the bigger picture. All those weird folders, config files, etc...

Learning React, Redux, JSS, etc for the first time was pretty rough. There were a lot of new paradigms thrown at me all at once. Took me a few months but I got comfortable eventually.

Docker and Kubernetes gave me a lot of trouble too. Docker was the easier of the two to grasp, but trying to combine them and get my own cluster set up was a lot of work. I bet the learning material and guides are a lot better these days. Kubernetes in particular was rough, because there were times where I didn't even know what to google. "If you know what you're looking for, inquiry is unneccesary. But if you don't know, how do you inqire?" 😛

A couple of things that are still giving me trouble: Microservices and event sourcing. Sort of in the same boat with those!

I'd say SOAP.

I was merely an 'user' for long, until I had to debug a patched version ot a custom library... well after that I made a mental folder of things you learn to avoid doing the same mistake in the future.

When Typescript started "taking off", I was like... wut?

React for me.

I was very familiar with using JS on a website, so I thought React would be an easy transition. Nope. What stung me was:

• React is compiled locally. If you're not used to that and how it works then its a pain to get started. When I learnt JQuery ages ago I started with something very, very small eg $(".mydiv).text("hello world");. This worked and I was able to build upon that and create more and more complex DOM manipulations from there. With React you can't just start with that one line.
• React has a lot of dependancies that don't make sense at first. Node, npm, React-DOM. In most beginner React tutorials there is little to no explanation of these. Initially I thought I would have to learn Node.js in and out before I learnt React - and that's a totally different kettle of fish.
• React tutorials are inconsistant. Some are very old, some predate React Hooks, some use TypeScript, some don't use Create React App, some presume prior knowledge of things like Redux.
• It's not intuitive to actually deploy a React component or app up on a live site. Most React tutorials end at the point where you've completed the app on your local machine... cool, but now what? How do I actually get it on my site?

For me it was DNS configuration for domains. I was wise to take some time to learn how it works in order to be able to debug it. Now ten years later I'm still explaining it to my colleagues :)

Currently trying to find my feet within the AWS ecosystem - it's huge, and oftentimes pretty confusing ... other more or less "hard" subjects:

• CSS (especially layout, the myriad ways to do it)
• testing/TDD (not to learn it or to do it, but to do it properly, and to keep doing it)

I have a heavy Frontend background it felt easy to me and I was afraid of backend, then I moved into backend, boyyyy was I wrong, backend web development is 1000x easier than frontend, no idea why the pay is better. Then I became a solid fullstack. Then later manager. So back to the question dynamic programming challenges are insane I don't get it and it hurts my brain, also binary operations. The most difficult thing I came across my career so far was in gaming client side predictions and server reconcilliation, also everything with geometry I struggle, like calculating the sum or two angles etc. seems like learning formulas by heart but understanding is tricky. Yeah the more you know the more you know you don't know and impostor syndrome grows bigger.