Module tasks

Intermediate operations that filter, transform, or process feed items.

Tasks apply to a Feed and yield a new feed, so they chain freely into longer pipes. Items are processed lazily, sequentially and in source order, unless a task reorders them or wraps another to run it concurrently, trading output order for throughput. Tasks buffering the whole feed in memory never complete on infinite sources.

Custom Tasks are functions that transform async iterables by returning async generator functions; items to be dropped are left unyielded or yielded as undefined, as feeds never carry it:

import { pipe } from '@metreeca/flow';
import { items } from '@metreeca/flow/feeds';
import { toArray } from '@metreeca/flow/sinks';
import type { Task } from '@metreeca/flow';

function double<V extends number>(): Task<V, V> {
  return async function* (source) {
    for await (const item of source) { yield item*2 as V; }
  };
}

await pipe(
  (items(1, 2, 3))
  (double())
  (toArray())
);  // [2, 4, 6]

Functions

batch: Creates a task collecting consecutive items into fixed-size batches.
concurrent: Creates a task interleaving several runs of another task over the same feed.
distinct: Creates a task discarding repeated items.
filter: Creates a task retaining only the items matching a predicate.
flatMap: Creates a task expanding each item into a data source.
group: Creates a task collecting items sharing the same key.
map: Creates a task converting each item into a new value.
peek: Creates a task observing the feed without altering it.
skip: Creates a task discarding a prefix of the feed.
sort: Creates a task reordering the feed.
take: Creates a task truncating the feed to a prefix.

Module tasks

Functions

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