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Module

x/better_iterators/mod.ts>LazyAsync

Chainable iterators (sync and async) for TypeScript, with support for opt-in, bounded parallelism
NfNitLoop/better-iterators
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class LazyAsync
implements AsyncIterable<T>, LazyShared<T>
import { LazyAsync } from "https://deno.land/x/better_iterators@v1.1.0/mod.ts";

Constructors

new
private
LazyAsync(iter: AsyncIterable<T>)

Methods

also(fn: (t: T) => void): LazyAsync<T>

Injects a function to run on each T as it is being iterated.

associateBy<Key>(uniqueKeyFn: Transform<T, Key>): Promise<Map<Key, T>>

Given uniqueKeyFn, use it to extract a key from each item, and create a 1:1 map from that to each item.

filter(f: Filter<T>): LazyAsync<T>

Keeps only items for which f is true.

first(): Promise<T>

Get the first item. @throws if there are no items.

firstOr<D>(defaultValue: D): Promise<T | D>

Get the first item. Returns defaultValue if there is no first item.

flatten(): LazyAsync<Flattened<T>>

Flattens a Lazy<Iterable> to a Lazy

groupBy<Key>(keyFn: Transform<T, Key>): Promise<Map<Key, T[]>>

Given keyFn, use it to extract a key from each item, and create a Map grouping items by that key.

limit(count: number): LazyAsync<T>

Limit the iterator to returning at most count items.

map<Out>(transform: Transform<T, Awaitable<Out>>): LazyAsync<Out>

Apply transform to each element.

Works like Array#map.

mapPar<Out>(max: number, transform: Transform<T, Promise<Out>>): LazyAsync<Out>

Like map, but performs up to max operations in parallel.

Note: This function will ensure that the order of outputs is the same as the order of the inputs they were mapped from. This can introduce head-of-line blocking, which can slow performance. If you don't need this, use mapParUnordered instead.

mapParUnordered<Out>(max: number, transform: Transform<T, Promise<Out>>): LazyAsync<Out>

A version of mapPar that does not enforce ordering, so doesn't suffer from head-of-line blocking.

partition(f: Filter<T>): Promise<Partitioned<T>>

Partition items into matches and others according to Filter f.

skip(count: number): LazyAsync<T>

Skip (up to) the first count elements

toArray(): Promise<T[]>

Collect all items into an array.

[Symbol.asyncIterator](): AsyncIterator<T>

Static Methods

from<T>(iter: AsyncIterable<T>): LazyAsync<T>

This lets you directly create an AsyncIterable, but you might prefer the shorter lazy function.