DCE Demo Discussions: custom-element by Sasha Firsov

[Westbrook]

As presented on 18 March to the WCCG, custom-element is a proposed approach to declarative custom elements by @sashafirsov.

Links to docs TK as available.

Further discussion and questions below.

[sashafirsov]

Live demo link

The primary differentiation of custom-element from other POCs on conceptual level:

• security focus: NO-JS app injection.
• fully funstional semantics: template, browser APIs(storage, routing, networking), reactive ( events, state management )

It is not a DX or UX solution, rather closing the gap in Cyber Security on the web standard level.

[matthewp]

I love it.

[JRJurman]

On the surface this feels very different from existing Web Components, I would be curious to know / see the mapping from the APIs exposed here and those APIs in Web Components.

It would be also great to know what novel new stuff exists here, that isn't possible in class-based implementations, and what we imagine those implementations would look like if you wanted to build the class-based version.

[sashafirsov]

@JRJurman, The class-based implementation implied JS, which is a

• not declarative syntax, hence should not be in the scope of Declarative Custom Element. Perhaps inline declaration is proper definition.
• It is not a streaming parser friendly, i.e. antipattern in HTML treatment.
• as JS is involved, it is not cross-vendor DCE code safe.
• I do not see the ability to do the initialization during the parsing by class-based implementation. In DCE it is a natural.
• SSR, dynamic (re-)hydration , state sharing with JS in equation would require server side browser engine. With DCE that is not needed.

[sashafirsov]

@JRJurman

mapping from the APIs exposed here and those APIs in Web Components.
There is no mapping. Lifecycle is different and spread between tiers. The "API" as JS API is not applicable either. There is no "methods" or "properties".

custom-element does use the WC convention internally. But exposing itself as one. Like the class, observedAttributes, events, etc. But it is not a part of DCE concept to be changed. Developers can extend DCE via WC registry though. And add any JS code to this class.