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map_values.ts
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map_values.ts
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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
// This module is browser compatible.
/**
* Applies the given transformer to all values in the given record and returns a new record containing the resulting keys
* associated to the last value that produced them.
*
* Example:
*
* ```ts
* import { mapValues } from "https://deno.land/std@$STD_VERSION/collections/mod.ts";
* import { assertEquals } from "https://deno.land/std@$STD_VERSION/testing/asserts.ts";
*
* const usersById = {
* 'a5ec': { name: 'Mischa' },
* 'de4f': { name: 'Kim' },
* }
* const namesById = mapValues(usersById, it => it.name)
*
* assertEquals(namesById, {
* 'a5ec': 'Mischa',
* 'de4f': 'Kim',
* });
* ```
*/
export function mapValues<T, O>(
record: Readonly<Record<string, T>>,
transformer: (value: T) => O,
): Record<string, O> {
const ret: Record<string, O> = {};
const entries = Object.entries(record);
for (const [key, value] of entries) {
const mappedValue = transformer(value);
ret[key] = mappedValue;
}
return ret;
}