> You can use the swap data attribute to update several fragments (imagine a saved icon) in several places declaratively.

Yeah, but why? The javascript snippet to accomplish the same is absolutely trivial and avoids a dependency.

> The price to pay for this is it does not work offline. For quickly prototyping and app it is very fast.

The true price is that you've now rewritten your HTML code in a non-standard DSL and are forever dependent on a third party library, and all that to accomplish a goal that seems entirely aesthetic to me.