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map_entries.ts
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map_entries.ts
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// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
/**
* Applies the given transformer to all entries in the given record and returns a new record containing the results
*
* Example:
*
* ```ts
* import { mapEntries } from "./map_entries.ts";
* import { assertEquals } from "../testing/asserts.ts";
*
* const usersById = {
* 'a2e': { name: 'Kim', age: 22 },
* 'dfe': { name: 'Anna', age: 31 },
* '34b': { name: 'Tim', age: 58 },
* } as const;
*
* const agesByNames = mapEntries(usersById,
* ([ id, { name, age } ]) => [ name, age ],
* )
*
* assertEquals(agesByNames, {
* 'Kim': 22,
* 'Anna': 31,
* 'Tim': 58,
* })
* ```
*/
export function mapEntries<T, O>(
record: Readonly<Record<string, T>>,
transformer: (entry: [string, T]) => [string, O],
): Record<string, O> {
const ret: Record<string, O> = {};
const entries = Object.entries(record);
for (const entry of entries) {
const [mappedKey, mappedValue] = transformer(entry);
ret[mappedKey] = mappedValue;
}
return ret;
}