Module sinks

Terminal operations that consume feeds and produce final results.

Sinks close a pipe: applying one to a Feed triggers execution and returns a promise resolving to the final result. Those that can decide their outcome early stop consuming rather than draining the source, while those collecting items into a container return it deeply immutable, freezing the container together with the items, keys and values collected into it. Those reducing the feed to a single value, whether computed over its items or selected among them, resolve to undefined when the feed carries none and no result is defined, leaving the choice of a fallback to the caller.

Custom Sinks are functions that consume async iterables by returning a promise for the final result:

import { pipe } from '@metreeca/flow';
import { items } from '@metreeca/flow/feeds';
import type { Sink } from '@metreeca/flow';

function histogram<V>(): Sink<V, Map<V, number>> {
  return async source => {
    const counts = new Map<V, number>();
    for await (const item of source) { counts.set(item, (counts.get(item) ?? 0)+1); }
    return counts;
  };
}

await pipe(
  (items("a", "b", "a"))
  (histogram())
);  // Map(2) { "a" => 2, "b" => 1 }

Functions

avg: Creates a sink averaging the items of the feed.
count: Creates a sink counting the items of the feed.
every: Creates a sink reporting whether every item matches a predicate.
find: Creates a sink retrieving the first item matching a predicate.
forEach: Creates a sink handing every item to a consumer.
max: Creates a sink selecting the greatest item of the feed.
min: Creates a sink selecting the least item of the feed.
reduce: Creates a sink reducing the feed to a single value, with or without an initial value.
some: Creates a sink reporting whether some item matches a predicate.
sum: Creates a sink summing the items of the feed.
toArray: Creates a sink collecting the items of the feed into an array.
toMap: Creates a sink collecting items or extracted values into a map under extracted keys.
toObject: Creates a sink collecting items or extracted values into a deeply immutable object under extracted keys.
toSet: Creates a sink collecting the distinct items of the feed into a set.
toString: Creates a sink joining the items of the feed into a string.

Module sinks

Functions

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