map_values.ts

// 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;
}