ts-prime/src/mapRecord.ts

A utility library for JavaScript and Typescript.

import { Pred } from './_types';
import { purry } from './purry';

/**
 * Loops each record element and maps against provided function.
 * @param record The target object.
 * @param fn Mapping function.
 * @returns The new record.
 * @signature
 *    P.flatMapRecord(record, fn)
 * @signature
 *    P.flatMapRecord(record, fn)
 * @example
 *    P.flatMapRecord({ a: 1, b: 2, c: 3 }, ([k,v]) => [[k, v * 2], [k + "_abc", v * 2]]) // => { a: 2, a_abc: 2, b: 4, b_abc: 4, c: 6, c_abc: 6 }
 *    P.flatMapRecord({ a: 1, b: 2, c: 3 }, ([k,v]) => [[k, v * 2], [k + "_abc", v * 2]]) // => { a: 2, a_abc: 2, b: 4, b_abc: 4, c: 6, c_abc: 6 }
 * @category Object, Pipe
 */
export function mapRecord<
  T extends Record<string, unknown>,
  K extends string,
  V
>(record: T, fn: Pred<[keyof T, T[keyof T]], [K, V]>): Record<K, V>;

export function mapRecord<
  T extends Record<string, unknown>,
  K extends string,
  V extends unknown
>(fn: (v: [keyof T, T[keyof T]]) => [K, V]): (record: T) => Record<K, V>;
export function mapRecord() {
  return purry(_mapRecord(), arguments);
}

const _mapRecord = () => <T extends { [k: string]: any }, K extends string, V>(
  rec: T,
  fn: (v: [keyof T, T[keyof T]]) => [K, V]
) => {
  return Object.entries(rec)
    .map(([k, v]) => {
      return fn([k as keyof T, (v as unknown) as T[keyof T]]);
    })
    .reduce((acc, [k, v]) => {
      acc[k] = v;
      return acc;
    }, {} as Record<K, V>);
};