[WorldMaker]

> 4. Observables (Ember, maybe Angular 2+?)

Don't forget Knockout which was the OG. You can also make the case that Svelte, Vue, and Qwik all are different takes on Observables (at least as much as Angular 2+ is) all with more or less magic and more or fewer escape hatches from Observable best practices to imperative(-looking) code.

I got a "What if we did Knockout but with with the compile-time benefits of TSX and Pure RxJS Observables?" itch a couple months back and have made some wild progress on it. I certainly don't think it is ready yet to advocate as an alternative to React, but it's probably in an interesting A4+B2 tangent on your map right here, and I find that interesting.

[jeremycarter]

I remember 2012, ASP.NET MVC Razor pages, combined with individual page knockout Js. Actually worked quite well. Infact that system is still running for that company. Sure we could have made a angularJS 1.0 SPA at the time, but knockout meant we only had to apply the pattern to the pages that needed it.

[WorldMaker]

I even used Durandal some in those cases where we really did want a SPA, but Knockout was good enough. That was something I appreciated about Knockout too was that the SPA framework was around it, not a part of it or implemented inside of it. Same with routing frameworks like Crossroads.js if you wanted something lighter than Durandal for just boring hash-navigation somewhere in the boundary spectrum between full SPA and MPA.

It was something that was also attractive about early React that React was similarly just a view engine and could do MPA or SPA or things in between and it didn't try to have the full kitchen sink. I don't know exactly where React stopped being that, but it always feels harder to argue that current React is "just" a view engine.

In the larger context here with this article, libraries that are just view engines should be great for building the internals of Web Components. (I'm hoping the view engine I've been working on might serve that role well, though with a dependency like RxJS I'm not sure if it would be towards the top of the list for many developers. It will certainly feel bigger than Lit, for example, no matter how well it tree shakes.)

[api]

I used Knockout to implement the very very very first ZeroTier network control dialog. Nice paradigm, but I think React beat it when things got really complex.

[recursive]

I got the same itch. Here's my thing. https://mutraction.dev/

[WorldMaker]

Interesting, thanks. Your mutation tracker isn't enough like "pure" RxJS Observables for my tastes and what I've been doing with my itch, but you captured a few of the things I'm covering in my system and are probably the next closest I've seen to what I've been doing (and I tried to research a deep dive). I think the only other thing is that I took an approach that observable change bindings look different from static HTML-like attributes. I did that in part because that's how Knockout used to do it, and also in part because I think it should better facilitate SSG/SSR/progressive enhancement when I get back around to those ideas (it's not a current priority, but definitely an idea I'm tracking).

[recursive]

I was also influenced quite a bit by knockout. SSR was explicitly not a goal of mine. To me, SSR as a feature in a framework like this is mostly interesting in the context of server/client continuity like rehydration. But I have a feeling the constraints imposed by anything like this aren't going to be worth it. If I was doing pure server rendering, flat text templates seem like the sweet spot, since it's fundamentally not interactive. Render to html string and ship it. And if I was doing that, I probably would not choose to use javascript or observables/signals.

[WorldMaker]

Knockout was designed in the heyday of the "progressive enhancement" era so it seems hard for me to claim a Knockout influence/inspiration if I'm not at least contemplating "progressive enhancement" of some sort. SSR isn't really my goal on that front but progressive enhancement/SSG (static site generation) certainly is a side goal for me (that's what I would like to have to self-host my own documentation site in something resembling the framework itself, rather than Jekyll or Docusaurus or whatever), but again not a main priority. It feels like the case for me where there is a lot of bleedover between SSR, SSG, and progressive enhancement and solving one basically solves all of them.

> I probably would not choose to use javascript or observables/signals.

This seems to be a case where we differ. In one obvious part because I don't tend to like signals and think they are very different from observables (because they are harder to encapsulate and offer fewer operators and tend to bleed too many accidental imperative escape hatches). Observables, to me, are just as useful to describe "open this file, read its contents, convert it from Markdown to HTML, then bind it to innerHTML here" on the server side as "fetch this URL, read its contents, convert it from Markdown to HTML, then bind it to innerHTML here" on the client side. Very different forms of interactivity, but there is still an interactivity there that a good observable pipeline can describe. Especially when you start to get into the idea that the difference between "open this file" and "fetch this URL" is tiny and can be dependency injected. Same component, slightly different inputs, slightly different expected outputs (you expect the server side binding to complete, whereas you expect the client side one to live for some time and continue to respond to different URLs from input).

[recursive]

I don't know much about the state of the art SSR/SSG, but in my mind, a whole document can be built synchronously, with a depth-first traversal of the templates/components. From that perspective the power and the constraints of reactive UI seem like overkill and limiting at the same time.

But anyway, the more UI frameworks, the more ideas get out there, the better. I'm hoping that some day in my lifetime, web UI gets "solved" and I'm not willing to believe that React is the answer. Does your project have a name yet? I'll keep an eye out.

[WorldMaker]

Just because on most modern hardware file I/O has millisecond latency and feels synchronous doesn't mean it is synchronous. It might feel like overkill to use Observables instead of Promises and I/O event loops or even thread-blocking faux synchronous file system calls, but there is still an asynchronous world there where it can be nice to have the full power of Observables. To be fair, my love affair with Observables started in C# in "backend" applications, so that's always been the natural fit for me and frontend and UI work has been the "side hustle" of taking stuff that I love in the backend side of the house and putting it to even more use.

I'm calling my view engine Butterfloat, and I only just finished the first documentation pass, so be gentle, but feedback is very welcome: https://github.com/WorldMaker/butterfloat