simple pick.js implementation

pick.js

// @flow

/**
 * Returns new object made of the picked paths.
 * Native implementation of lodash `pick`.
 * Shaves 1-2kb off download size: https://bundlephobia.com/result?p=lodash.pick@4.4.0.
 * @see https://github.com/you-dont-need/You-Dont-Need-Lodash-Underscore#_pick
 * @see https://lodash.com/docs/#pick
 * @return {Object}
 */
export default function pick(object: Object, paths: Array<string>): Object {
  const obj = {};
  paths.forEach((path) => {
    if (object[path]) {
      obj[path] = object[path];
    }
  });
  return obj;
}

pick.test.js

import pick from './pick';

test('pick() subset', () => {
  const subset = { a: 1, b: 2 };
  const superset = { ...subset, c: 3 };

  const picked = pick(superset, Object.keys(subset));

  expect(picked).toEqual(subset);
});

test('pick() superset', () => {
  const subset = { a: 1, b: 2 };
  const superset = { ...subset, c: 3 };

  const picked = pick({ ...subset }, Object.keys(superset));

  expect(picked).toEqual(subset);
});

test('pick() identity', () => {
  const set = { a: 1, b: 2 };

  const picked = pick({ ...set }, Object.keys(set));

  expect(picked).toEqual(set);
});


test('pick() no fields of empty object returns empty object', () => {
  const empty = {};

  const picked = pick({ ...empty }, []);

  expect(picked).toEqual(empty);
});


test('pick() missing fields of empty object returns empty object', () => {
  const missingFields = ['x', 'y', 'z'];
  const empty = {};

  const picked = pick({ ...empty }, missingFields);

  expect(picked).toEqual(empty);
});