reduce()

reduce: accumulate over the whole source, emit ONE final value on the source’s COMPLETE (RxJS reduce). Unlike {@link scan} (which emits every step), reduce stays quiet until the source terminates. completeWhenDepsComplete:false + terminalAsRealInput:true: the fn fires on the source COMPLETE (reading terminal===true) and emits the accumulator + COMPLETE. An empty source emits the seed (RxJS parity). A source ERROR auto-forwards (errorWhenDepsError default).

Import

import { reduce } from "@graphrefly/ts/operators";

Signature

function reduce(
  reducer: (acc: T, v: S) => T,
  seed: T,
): Operator<S, T>

Parameters

Parameter	Type	Description
reducer	(acc: T, v: S) => T	Reducer called with the accumulator and each upstream DATA value.
seed	T	Initial accumulator value emitted if the source completes empty.

Returns

An operator that emits one accumulated value when the source completes.

Example

import { graph } from "@graphrefly/ts/graph";
import { reduce } from "@graphrefly/ts/operators";

const total = graph().initNode(reduce((sum: number, value: number) => sum + value, 0), [source]);

Source

packages/ts/src/graph/operators.ts