@monstermann/fn/dist/array/findMapLastOrElse.js

A utility library for TypeScript.

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

//#region src/array/findMapLastOrElse.ts
/**
* `findMapLastOrElse(array, predicate, mapper, callback)`
*
* Finds the last element in `array` that satisfies the provided `predicate` function and applies the `mapper` function to it, returning a new array with the mapped element, or the result of calling `callback` with the array if no element is found.
*
* ```ts
* findMapLastOrElse(
*     [1, 2, 3, 4],
*     (x) => x > 10,
*     (x) => x * 10,
*     (arr) => arr.length,
* ); // 4
* ```
*
* ```ts
* pipe(
*     [1, 2, 3, 4],
*     findMapLastOrElse(
*         (x) => x > 10,
*         (x) => x * 10,
*         (arr) => arr.length,
*     ),
* ); // 4
* ```
*/
const findMapLastOrElse = dfdlT((target, predicate, mapper, orElse) => {
	const idx = target.findLastIndex(predicate);
	if (idx === -1) return orElse(target);
	const prev = target[idx];
	const next = mapper(prev, idx, target);
	if (is(prev, next)) return target;
	const result = cloneArray(target);
	result.splice(idx, 1, next);
	return result;
}, 4);

//#endregion
export { findMapLastOrElse };