heximal

I love that this lets you create custom elements! I think that's a big missing feature from HTMX (even though HTMX can already use custom elements). I'm working on a somewhat similar system called Heximal. It focuses on adding full-fledged templating to the <template> element, and full declarative component definitions to HTML, plus some built-in custom elements like <h-var>, <h-out>, <h-scope>, <h-include>, and <h-fetch> that make HTML more of a declarative programming language. A big difference from HTMX is that it doesn't rely on magic attributes, but instead adds full data-binding with rich expressions for any attribute or text content, and control flow, to <template>. And component definitions include defining properties, attributes, styles, etc. These things are being proposed for HTML, so Heximal is somewhat of a polyfill for HTML

I strongly agree with the premise of the article - HTML could be a fabulous substrate for computational notebooks! But I didn't love the choices for how to implement it here. Dynamic, reactive HTML can be a lot more declarative than this, and Observable is cool, but strays from standard JS. I started to build a reactive HTML system called Heximal that eventually will have notebook support, but it's declarative, based on HTML templates and custom elements with a expression / reactivity system (based on the TC39 Signals proposal) on top. https://github.com/elematic/heximal It's a bit like a mashup of HTMX, Tangle, Curvenote, and Polymer. Or like HTML if were natively reactive. I think it will lend it self to graphical editing and notebook user cases quite well.

The original author of Lit recently left Google and is working on something very similar to this AFAIK. https://github.com/elematic/heximal