Very nearly[1] every current framework now has a similar concept, all with the same general foundation: some unit of atomic state, some mechanism to subscribe to its state changes by reading it in a tracking context, and some internal logic to notify those subscriptions when the state is written. They all have a varied set of related abstractions that build upon those fundamental concepts, which…
> But frankly, I doubt it, if it was that similar, why are there at least a dozen frameworks with their own version?*
… is part of what distinguishes each such framework. Another part is that state management and derived computations are only part of what any of the frameworks do. They all have, beyond their diverse set of complementary reactive abstractions, also their own varied takes on templating, rendering models, data fetching, routing, composition, integration with other tools and systems.
Moreover, this foundational similarity between the frameworks is relatively recent. It’s a convergence around a successful set of basic abstractions which in many ways comes from each framework learning from the others. And that convergence is so pervasive that it’s motivating the standardization effort.
This especially stands out because the reference polyfill is derived from Angular’s implementation, which only very recently embraced the concept. From reading the PR notes, the implementation has only minor changes to satisfy the proposed spec. That’s because Angular’s own implementation, being so recent, internalizes many lessons learned from prior art which also inform the thinking behind the spec itself.
This is very much like the analogy to Promises, which saw a similar sea change in convergence around a set of basic foundational concepts after years of competing approaches eventually drifting in that same direction.
[1]: Most notably, React is unique in that it has largely avoided signals while many frameworks inspired by it have gravitated towards them.
