/
map_keys.ts
40 lines (37 loc) · 1.06 KB
/
map_keys.ts
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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
// This module is browser compatible.
/**
* Applies the given transformer to all keys in the given record's entries and
* returns a new record containing the transformed entries.
*
* If the transformed entries contain the same key multiple times, only the last
* one will appear in the returned record.
*
* @example
* ```ts
* import { mapKeys } from "https://deno.land/std@$STD_VERSION/collections/map_keys.ts";
* import { assertEquals } from "https://deno.land/std@$STD_VERSION/assert/assert_equals.ts";
*
* const counts = { a: 5, b: 3, c: 8 };
*
* assertEquals(
* mapKeys(counts, (it) => it.toUpperCase()),
* {
* A: 5,
* B: 3,
* C: 8,
* },
* );
* ```
*/
export function mapKeys<T>(
record: Readonly<Record<string, T>>,
transformer: (key: string) => string,
): Record<string, T> {
const ret: Record<string, T> = {};
for (const [key, value] of Object.entries(record)) {
const mappedKey = transformer(key);
ret[mappedKey] = value;
}
return ret;
}