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scanObservablePipe

Alternative: scan$$$

Inlined: scanObservable, scan$$

Types​

function scanObservablePipe<GIn, GOut>(
  scanFunction: IScanFunction<GIn, GOut>,
  initialValue: GOut,
): IObservablePipe<GIn, GOut>

Definition​

Applies an accumulator (or "reducer function") to each value from the source Observable from an initial value (second argument). This accumulated value is then emitted.

Diagram​

Algorithm​

OUTscanObservablePipe(reducer, accumulatedValue)observableOUTscanObservablePipe(reducer, accumulatedValue)observableaccumulatedValue = reducer(accumulatedValue, value)loop[for each incoming value]valueaccumulatedValue

Example​

OUTscanObservablePipe((a, b) => (a + b), 0)observableOUTscanObservablePipe((a, b) => (a + b), 0)observable00112336

Example​

Compute the sum of incoming values​

const subscribe = pipe$$(of(0, 1, 2, 3), [
  scan$$$((sum: number, value: number): number => {
    return sum + value;
  }, 0),
]);

subscribe((value) => {
  console.log(value);
});

Output:

0
1
3
6