Modeling an election in JavaScript

election.js

/**
 * Dependencies
 */
const sortBy = require('sort-by');

/**
 * Representing an election as a data structure
 */
const votes = [
  { id: 0, voterId: 'a', zone: 'Oslo', party: 'Miljøpartiet De Grønne' },
  { id: 1, voterId: 'b', zone: 'Oslo', party: 'Fremskrittspartiet' },
  { id: 2, voterId: 'c', zone: 'Oslo', party: 'Arbeiderpartiet' },
  { id: 3, voterId: 'd', zone: 'Oslo', party: 'Piratpartiet' },
  { id: 4, voterId: 'e', zone: 'Oslo', party: 'Liberalistene' },
  { id: 5, voterId: 'f', zone: 'Oslo', party: 'Høyre' },
  { id: 6, voterId: 'g', zone: 'Oslo', party: 'Sosialistisk Venstreparti' },
  { id: 7, voterId: 'h', zone: 'Oslo', party: 'Venstre' },
  { id: 8, voterId: 'i', zone: 'Oslo', party: 'Piratpartiet' },
  { id: 9, voterId: 'j', zone: 'Oslo', party: 'Høyre' },
  { id: 10, voterId: 'k', zone: 'Oslo', party: 'Høyre' },
  { id: 11, voterId: 'l', zone: 'Trondheim', party: 'Miljøpartiet De Grønne' },
  { id: 12, voterId: 'm', zone: 'Trondheim', party: 'Fremskrittspartiet' },
  { id: 13, voterId: 'n', zone: 'Trondheim', party: 'Arbeiderpartiet' },
  { id: 14, voterId: 'o', zone: 'Trondheim', party: 'Piratpartiet' },
  { id: 14, voterId: 'o', zone: 'Trondheim', party: 'Piratpartiet' },
  { id: 15, voterId: 'p', zone: 'Trondheim', party: 'Piratpartiet' },
  { id: 16, voterId: 'q', zone: 'Bergen', party: 'Liberalistene' },
  { id: 17, voterId: 'r', zone: 'Bergen', party: 'Høyre' },
  { id: 18, voterId: 's', zone: 'Bergen', party: 'Sosialistisk Venstreparti' },
  { id: 19, voterId: 't', zone: 'Bergen', party: 'Sosialistisk Venstreparti' },
  { id: 20, voterId: 'u', zone: 'Bergen', party: 'Venstre' },
  { id: 21, voterId: 'v', zone: 'Bergen', party: 'Piratpartiet' },
  { id: 22, voterId: 'x', zone: 'Stavanger', party: 'Piratpartiet' },
  { id: 23, voterId: 'y', zone: 'Stavanger', party: 'Piratpartiet' },
  { id: 24, voterId: 'z', zone: 'Stavanger', party: 'Piratpartiet' },
  { id: 25, voterId: 'æ', zone: 'Stavanger', party: 'Piratpartiet' },
  { id: 26, voterId: 'ø', zone: 'Stavanger', party: 'Piratpartiet' },
  { id: 27, voterId: 'å', zone: 'Stavanger', party: 'Piratpartiet' },
];

/**
 * Selection of fields (mapping)
 */
const voteIds = votes.map((vote) => vote.id);
const voterIds = votes.map((vote) => vote.voterId);
const zones = votes.map((vote) => vote.zone);
const parties = votes.map((vote) => vote.party);

/**
 * Counting the amount of votes
 */
const amountOfVotes = votes.length;

/**
 * Getting the sum for a specific party
 */
const amountOfVotesForPiratpartiet = votes
.filter((vote) => vote.party === 'Piratpartiet')
.length;

/**
 * Function that takes a list and an element
 * and returns a new list of unique elements
 */
function uniqueReducer(uniqueList, element) {
  return uniqueList.includes(element) ?
  uniqueList :
  [...uniqueList, element];
}

/**
 * Getting all the unique parties that are represented
 */
const partiesRepresented = votes
.map((vote) => vote.party)
.reduce(uniqueReducer, []);

/**
 * Getting all the unique zones that are represented
 */
const zonesRepresented = votes
.map((vote) => vote.zone)
.reduce(uniqueReducer, []);

/**
 * Group all the votes by party
 */
const votesGroupedByParty = votes
.reduce((votesByParty, vote) => {
  return Object.assign({}, votesByParty, {
    [vote.party]: [
      ...(votesByParty[vote.party] || []),
      vote,
    ],
  });
}, {});

/**
 * Group all the votes by zone
 */
const votesGroupedByZone = votes
.reduce((votesByZone, vote) => {
  return Object.assign({}, votesByZone, {
    [vote.zone]: [
      ...(votesByZone[vote.zone] || []),
      vote,
    ],
  });
}, {});

/**
 * Find the national winner party by counting all the votes per party
 */
const nationalWinner = partiesRepresented
.map((party) => ({ party, sum: votesGroupedByParty[party].length }))
.sort(sortBy('-sum'))
.map((result) => result.party)[0]

/**
 * Find a summary of each zone
 */
const summaryByZone = zonesRepresented
.map((zone) => {
  return {
    zone: zone,
    sums: partiesRepresented
    .map((party) => ({
      party,
      sum: votesGroupedByZone[zone]
      .filter((vote) => vote.party === party)
      .length
    }))
  };
});

/**
 * Find the winner for each zone
 */
const winnerByZone = summaryByZone
.map((summary) => ({
  zone: summary.zone,
  winner: summary.sums
  .sort(sortBy('-sum'))
  .map((result) => result.party)[0]
}));