@monstermann/fn/dist/map/mapEach.js

A utility library for TypeScript.

import { is } from "../function/is.js";
import { dfdlT } from "@monstermann/dfdl";
import { cloneMap } from "@monstermann/remmi";

//#region src/map/mapEach.ts
/**
* `mapEach(map, fn)`
*
* Maps each value in `map` using `fn`, returning a new map with the transformed values.
*
* ```ts
* mapEach(
*     new Map([
*         ["a", 1],
*         ["b", 2],
*     ]),
*     (value, key) => value * 2,
* ); // Map(2) { "a" => 2, "b" => 4 }
* ```
*
* ```ts
* pipe(
*     new Map([
*         ["a", 1],
*         ["b", 2],
*     ]),
*     mapEach((value, key) => value * 2),
* ); // Map(2) { "a" => 2, "b" => 4 }
* ```
*/
const mapEach = dfdlT((target, fn) => {
	let result;
	for (const [k, prev] of target) {
		const next = fn(prev, k, target);
		if (is(prev, next)) continue;
		result ??= cloneMap(target);
		result.set(k, next);
	}
	return result ?? target;
}, 2);

//#endregion
export { mapEach };