Building a Standalone Vue 3 Reactivity Library: CycleJS‑like Reactive View, Immer‑like State, RxJS‑like Operators, and React‑Hooks‑like Mechanisms

The author begins by noting the release of Vue's Function‑based API RFC, comparing it to React hooks and emphasizing its value‑enhancement approach rather than function‑enhancement, and introduces the Advanced Reactivity API as a more expressive primitive.

Using this API, a minimal reactive library is built from scratch: a watchable function that turns any object or array into a watchable structure, recursive state and value constructors, and functional helpers fmap , ap , and bind that treat reactive values as functors and monads.

With these building blocks, the author creates a CycleJS‑like reactive view by combining reactive values into a view$ stream, enabling automatic UI updates without explicit setState calls. A simple Counter component and a more complex TodoApp illustrate how reactive state can drive component rendering, leveraging combineArray , combineObject , and a generic combine function to wrap arbitrary structures into reactive values.

The library also provides an immer‑like immutable update mechanism: combineArray returns immutable lists via copy‑on‑write, allowing safe structural sharing and efficient diffing similar to immer .

To emulate RxJS behavior, a pipe function and operators such as mapx , filter , take , and scan are implemented using the same functional primitives, enabling reactive streams that can be composed and transformed.

Finally, the article shows how to recreate React‑hooks concepts (e.g., useEffect , useRef , useReactive ) on top of the reactivity API by introducing enhancers ( resumable , referencable , reactive ) that manage lifecycle, storage, and re‑execution, culminating in an interval demo that produces an automatically updating counter.

The author concludes that while the demos prove the versatility of Vue's reactivity primitives, the current implementation is coarse, lacks proper unwatch handling, and should not be used in production; it serves only as a conceptual showcase for building more complete libraries.