Pick in object

pickInObject.js

/* ------------------------------------------
   Pick in object
--------------------------------------------- */
const peek = (...keep) => iter => keep.indexOf(iter) > -1;
const split = c => c.split('.');
const tail = array => {
  const [head, ...result] = array; // eslint-disable-line
  return result;
};

/* eslint-disable no-confusing-arrow */
const pickInObject = (...fields) => object => {
  if (!object) { return object; }

  const levels = fields.map(split);
  const currentLevel = levels
    .filter(c => c.length === 1)
    .map(c => c[0]);

  const rec = levels
    .filter(c => c.length > 1)
    .filter(c => Object.prototype.hasOwnProperty.call(object, c[0]))
    .reduce((acc, c, i, xs) => {
      const next = {
        ...acc,
        [c[0]]: [
          ...acc[c[0]] || {},
          tail(c).join('.'),
        ],
      };
      return (i === xs.length - 1)
        ? Object.keys(next)
          .map(d => [d, next[d]])
        : next;
    }, [])
    .reduce((acc, c) => ({
      ...acc,
      [c[0]]: {
        ...acc[c[0]],
        ...pickInObject(...c[1])(object[c[0]]),
      },
    }), {});

  const res = Object.keys(object)
    .filter(peek(...currentLevel))
    .reduce((acc, k) => ({
      ...acc,
      [k]: object[k],
    }), {});

  return Object.assign({}, res, rec);
};

export default pickInObject;

pickInObject.spec.js

import pickkInObject from './pickInObject';

describe('Peek in object helper on chanceProfile module', () => {
  describe('pickInObject', () => {
    it('should peek id, name from the provided object', () => {
      const res = pickInObject('id', 'name')({
        id: 'id',
        name: 'name',
      });
      expect(Object.keys(res).join('')).toBe('idname');
    });
    it('should peek nested information from the provided object', () => {
      const res = pickInObject('nested.test')({
        nested: {
          test: 'test',
        },
      });
      expect(res.nested.test).toBe('test');
    });
    it('should peek very nested information from the provided object', () => {
      const res = pickInObject('properties.nested.veryNested.veryVeryNested.value')({
        properties: {
          nested: {
            veryNested: {
              veryVeryNested: {
                value: true,
              },
            },
          },
        },
      });
      expect(res.properties.nested.veryNested.veryVeryNested.value)
        .toBe(true);
    });
    it('should return empty object if peek is empty from the provided object', () => {
      const res = pickInObject()({
        id: 'id',
        name: 'name',
      });
      expect(res).toEqual({});
    });
    it('should return empty object if peek is empty from an empty object', () => {
      const res = pickInObject()({});
      expect(res).toEqual({});
    });
    it('should return null if object is null', () => {
      const res = pickInObject()(null);
      expect(res).toBeNull();
    });
    it('should return empty object if object is undefined', () => {
      const res = pickInObject()();
      expect(res).toBe(undefined);
    });
  });
});

usage.js

import pickkInObject from './pickInObject';

const res = peekInObject(
  'id', 'properties.birth', 'devices.mobile', 'properties.nested.very', 'properties.nested.veryNested.re', 'properties.location'
)({
  id: 'id',
  name: 'name',
  properties: {
    birth: 'birth value',
    location: 'rio',
    nested: {
      very: true,
      veryNested: {
        re: true,
      },
    },
  },
  devices: {
    mobile: true,
    desktop: false,
  },
});
console.log(res)