Function useCurrent

Subscribe to a live source and return the current value of a reducer mapping, updated on a throttle. Equivalent to useSnapshot(src).tail(tail).reduce(mapping) but with one subscription, one memo, and narrow per-entry types inherited from TimeSeries.reduce.

const current = useCurrent(live, { cpu: 'avg', host: 'unique' });
//   ^ { cpu: number | undefined;
//       host: ReadonlyArray<ScalarValue> | undefined }

const recent = useCurrent(live, { cpu: 'p95' }, { tail: '30s' });
Copy

Returns a stable-shape object while the source has no events (every mapped field is undefined), so destructuring on first render is safe.

Reference stability: when a new event push leaves the reduce output structurally unchanged (same scalar values, same-length arrays with same elements), the previous result reference is returned unchanged. Downstream useMemo([value]) and useEffect([value]) only re-run when the value actually changes — no need for a manual .slice() or deep-compare equality helper at the call site.