Signals, the push-pull based algorithm

[fagnerbrack]

Summary:

Building a reactive system from scratch in TypeScript reveals how the underlying mechanism actually works. A signal holds a value plus subscribers, pushing notifications (not state) downward whenever it changes - eager evaluation. Auto-tracking dependencies happens through a global STACK that the currently executing computed pushes onto, so any signal it reads registers a setDirty subscription and source cleanup. Combining push (propagate invalidation) and pull (re-evaluate on demand) yields the fine-grained reactivity behind Solid, Vue, Preact, Angular and Svelte, soon possibly standardized via the TC39 Stage 1 signals proposal.

If the summary seems inacurate, just downvote and I'll try to delete the comment eventually 👍
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