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

A utility library for TypeScript.

import { dfdlT } from "@monstermann/dfdl";

//#region src/array/indexBy.ts
/**
* `indexBy(target, by, transform?)`
*
* Creates a record by indexing the `target` array using the `by` function to generate keys. Optionally transforms values using the `transform` function.
*
* ```ts
* const users = [
*     { id: 1, name: "Alice" },
*     { id: 2, name: "Bob" },
* ];
*
* indexBy(users, (user) => user.id);
* // { 1: { id: 1, name: 'Alice' }, 2: { id: 2, name: 'Bob' } }
*
* indexBy(
*     users,
*     (user) => user.id,
*     (user) => user.name,
* ); // { 1: "Alice", 2: "Bob" }
* ```
*
* ```ts
* pipe(
*     users,
*     indexBy((user) => user.id),
* ); // { 1: { id: 1, name: 'Alice' }, 2: { id: 2, name: 'Bob' } }
*
* pipe(
*     users,
*     indexBy(
*         (user) => user.id,
*         (user) => user.name,
*     ),
* ); // { 1: "Alice", 2: "Bob" }
* ```
*/
const indexBy = dfdlT((target, by, transform) => {
	return target.reduce((acc, value, idx) => {
		const key = by(value, idx, target);
		acc[key] = transform ? transform(value, key, idx, target) : value;
		return acc;
	}, {});
}, (args) => Array.isArray(args[0]));

//#endregion
export { indexBy };