Go to Latest
File
// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
import { mapEntries } from "./map_entries.ts";
/** * Applies the given aggregator to each group in the given Grouping, returning the results together with the respective group keys * * ```ts * import { aggregateGroups } from "https://deno.land/std@$STD_VERSION/collections/mod.ts"; * import { assertEquals } from "https://deno.land/std@$STD_VERSION/testing/asserts.ts"; * * const foodProperties = { * 'Curry': [ 'spicy', 'vegan' ], * 'Omelette': [ 'creamy', 'vegetarian' ], * } * const descriptions = aggregateGroups(foodProperties, * (current, key, first, acc) => { * if (first) * return `${key} is ${current}` * * return `${acc} and ${current}` * }, * ) * * assertEquals(descriptions, { * 'Curry': 'Curry is spicy and vegan', * 'Omelette': 'Omelette is creamy and vegetarian', * }) * ``` */export function aggregateGroups<T, A>( record: Readonly<Record<string, Array<T>>>, aggregator: (current: T, key: string, first: boolean, accumulator?: A) => A,): Record<string, A> { return mapEntries( record, ([key, values]) => [ key, // Need the type assertions here because the reduce type does not support the type transition we need values.reduce( (accumulator, current, currentIndex) => aggregator(current, key, currentIndex === 0, accumulator), undefined as A | undefined, ) as A, ], );}