Code Your Future JS Core 3 Project

Installation

Clone this repo using the command

git clone https://github.com/Buroni/cyf-election.git

Introduction

After a recent referendum, London has gained independence from the rest of the UK. A snap election will be held in a month to decide who will be the leader of the new country. You have been asked to implement an electronic voting system in javascript which allows the government to easily register voters into the system, filter out invalid votes and calculate who the winning candidate is.

The three files you will be working on during this project are the following:

• election.js - Contains all of the functions required to carry out the election process. From part 2 onwards this file will be modularised into classes.
• index.html - Displays the election results. From part 2 onwards this file will also take user input.
• voters.json - The "real" voter data. This file will not appear until the election occurs at part 3.

In order to make the project more manageable, it has been broken down into three parts. They are outlined below.

• Part 1: write the functions required to carry out the election process, and allow the results with a small amount of sample data to be displayed on a HTML page.
• Part 2: re-organise the functions into three classes: Voter, Candidate and Election, and improve the voter validation process. Allow new voters to be inputted via a HTML page.
• Part 3 (election time): run the election on a large population stored as a JSON file.

Voter Data Format

Have a look at the sample voter data provided in election.js. You will notice that the voters are stored as an array of objects, and that their voting card is an array of integers. Each integer in the votingCard array represents a candidate id where each ID has double the weight of the ID on its right.

So for example, if my votingCard array is [1,3,2] I cast 1 vote for candidate 1, I cast 0.5 votes for candidate 3 and 0.025 votes for candidate 2.

Candidate Data Format

Now look at the sample candidate data. Like the voter data, each candidate is stored as an object but with some different properties. You should also notice that unlike the voter data which is stored as an array of objects, the candidate data is stored as an object containing objects. Each object key represents the ID of the candidate. For example the candidate Tamara Faiza has candidate ID 1.

The numVotes property in each candidate object represents the number of votes that candidate received in the election. When a new instance of a candidate is created, their numVotes property should always be 0.

Part 1

Exercise 1

Candidates should also be able to vote in the election, however right now the format of candidates isn't such that we can just concatenate it onto the votingPopulation array.

Write a function candidatesObjToArray which takes the candidates object as input, and returns an array of candidates which can be joined onto votingPopulation.

Hint: You might find the map function useful.

Exercise 2

Before we worry about how to calculate the election results, we need to introduce some definition of an invalid voting card. Right now we regard a voting card as invalid if it contains more than two votes, or contains multiple votes for the same candidate.

Write a function filterInvalidVoters which removes any voters who have voted for more than 2 people, or have voted for the same person twice. This function should input the allVoters array, and return an array containing only valid voters.

Exercise 3

Right now all candidates have numVotes set to 0. Write a function runElection which takes the votingPopulation and candidates as arguments. The function should change the numVotes property of each candidate based on the voting cards of the voters, and return a candidates object with each candidate having an updated numVotes value.

Exercise 4

Write a function getWinner which taken the updated candidates object as input, and returns the candidate with the most votes if there is no draw. If there is a draw, the function should return null.

Exercise 5

Write a function printWinnerMessage whose input is the winner previously calculated by getWinner. This function should print "The election was a draw" if a draw occurred, otherwise it should print a message including the winner's name and how many votes he/she received.

Exercise 6

You have permission from the government to change people's voting cards because the real election hasn't occurred yet.

If the previous 5 exercises were completed correctly, you should see a message saying that Tamara Faiza has won the election with 3.5 votes. Change Nour al-Din's voting card from [4,1] to [4,3] and you should notice that a draw has occurred.