Ask HN: Should I learn Bootstrap 3 or 4 at this moment?

Me too!

Yes, I think that if you don't know CSS then learning that (rather than bootstrap 3 vs 4) is the right answer.

None of these technologies are all that hard. Like, they are easy enough that I don't understand it as a question...

if you know CSS/ SASS and that stack, they take about an hour to figure out the main points and get rolling. But even if you don;t know hardly any CSS then they still take like a day or so, and the principles are pretty much the same.

And equivalent question is "should I learn Sublime or Notepad++". If you understand what they do, pick one and if it stops being a thing you can use for whatever reason then learn the other, because the difficult part of understanding what id going on with them is conceptually the same between them.

The differences are not that big to make a difference in "learning".

If your question was should I use 3 or 4, then my answer would be, depends on your project.

But for learning, the version doesn't make much of a difference as the general principles are the same.

I think it's better to ignore the world of framework hype and just code to the browser APIs as described by the standards. You can basically guarantee that your site will still work ten years from now and that your knowledge will still be relevant (though you'll need to keep up to date with new features e.g. flexbox).

I personally find it more work to learn frameworks and deal with the leaky abstractions inherent in them than to work with the browser directly. Especially when I hit a case where I want to do something that the framework authors didn't cater for and I end up having to go down to the browser APIs to implement it anyway.

In the short term, it's a bigger investment to learn the underlying technologies, but in the long term it pays off big time, since you don't end up being stuck with something that sounded great two years ago when you started your project but is no longer maintained.

I'm a backend dev who did a little frontend here and there over a decade ago (and has sorta kept up since then out of curiosity). So I know CSS decently well, but still need to look things up here and there, and I certainly don't know all the bleeding-edge stuff.

So yes, you should learn CSS, at least so you understand how web technologies work, in general. But not learning/using Bootstrap (as the parent recommends), if you think that will make your life easier, seems silly. I recently had to do a couple frontend projects for the first time in said over-a-decade-ago, and I found Bootstrap easy to pick up (it took like a half hour), and made things a lot easier than rolling my own CSS, for very little cost.

To actually answer the OP's question, it depends on what you need to do. If you're starting new projects, just learn BS4. I did that back in February, and it worked out well for me. If you have to deal with some existing projects that use BS3, you'll of course need to learn that. But they're so easy to use, that if you already understand how HTML and CSS work (if you don't, of course that should be your step 1), you don't need to really "learn" it so much as read through the section on the layout model, and start building a page/site/app, looking at the reference docs as you go along when you want to add a dropdown or navbar or something.