CodeVetter · Repo Unpack · Data flow
pmndrs/zustand
State updates enter through values, updater functions, reducers, or middleware-wrapped setters. The vanilla store owns the resulting snapshot and notifies synchronous subscribers; React selects snapshots through its external-store interface. Persistence and DevTools create additional output and input boundaries around that same store.
- setState evaluates function input against current state, skips Object.is-identical results, then replaces or shallow-merges before notifying listeners with new and previous state.
- subscribe stores callbacks in a Set and returns deletion-based unsubscribe; getInitialState retains the initializer result separately from later state snapshots.
- useStore supplies selected getState snapshots for clients and selected getInitialState snapshots for server rendering, using the same api.subscribe boundary.
- Selective subscriptions cache currentSlice and pass next/previous slices only when equalityFn rejects equivalence; useShallow instead stabilizes the selected output reference.
- Persistence wraps both api.setState and the creator's set: each updates live state first, then partializes a shallow copy and writes a state/version envelope under options.name.
- createJSONStorage parses storage strings, awaits Promise reads, serializes writes with an optional replacer, and delegates removal to the selected adapter.
- Hydration checks stored versions, optionally migrates, merges with the latest available state, replaces live state, writes migrated data, and then signals completion unless its generation is obsolete.
- DevTools sends actions and current snapshots outward; incoming ACTION and DISPATCH messages can set state or dispatch reducers while setStateFromDevtools temporarily suppresses recording.