Immutable.JS groupBy example

groupby.ts

import * as Immutable from 'immutable';

interface Place {
  country: string;
  stateOrProvince: string;
  city: string;
}

const list: Immutable.List<Place> = Immutable.List<Place>([
  {country: 'USA', stateOrProvince: 'Michigan', city: 'Petoskey'},
  {country: 'USA', stateOrProvince: 'Michigan', city: 'Detroit'},
  {country: 'USA', stateOrProvince: 'Michigan', city: 'Cadillac'},
  {country: 'USA', stateOrProvince: 'Ohio', city: 'Akron'},
  {country: 'USA', stateOrProvince: 'Ohio', city: 'Dayton'},
  {country: 'Canada', stateOrProvince: 'Ontario', city: 'London'},
  {country: 'Mexico', stateOrProvince: 'Chihuahua', city: 'Juarez'},
  {country: 'Mexico', stateOrProvince: 'Chihuahua', city: 'Delicias'},
]);

const BLANK = '-';

const countryGrouper = (place: Place | undefined) => place ? place.country : BLANK;
const stateOrProvinceGrouper = (place: Place | undefined) => place ? place.stateOrProvince : BLANK;

const byCountry: Immutable.Map<string, Immutable.List<Place>> = Immutable.Map<string, Immutable.List<Place>>(list.groupBy(countryGrouper));
const byCountryAndStateOrProvince: Immutable.Map<string, Immutable.Map<string, Place>> = Immutable.Map<string, Immutable.Map<string, Place>>(byCountry.map((places: Immutable.List<Place> | undefined) => places ? places.groupBy(stateOrProvinceGrouper) : Immutable.Map()));

byCountryAndStateOrProvince.forEach((byStateOrProvince: any , country: any) => {
  console.log('Country', country);
  byStateOrProvince.forEach((places: Immutable.List<Place>, stateOrProvince: string) => {
    console.log('+ State or Province', stateOrProvince);
    places.forEach((place: Place | undefined) => console.log('+ + Place', place ? place.city : BLANK);
  });
});