Caritat counts votes. Caritat is designed only to provide the step from ballots to results. It provides no mechanism for people to cast votes; this is left to whatever code calls Caritat. A number of different counting mechanisms are provided:

• Simple plurality winner

• Approval voting

• Instant Runoff Voting

• Borda count

• Condorcet methods

  • Condorcet winner (only if one exists!)

  • Schulze method

• Single Transferable Vote

  • Meek method (see also the second paper)

Additional Condorcet and STV methods are on a TODO-list, as are party-list proportional representation multi-winner methods. (Chiefly D'Hondt, which is used for parliamentary elections in the author's country of origin.)

Boilerplate bores me. This is JavaScript code, which doesn't touch on anything to do with HTML or the DOM. So you're probably going to get it through npm and use it in a node.js program somewhere. If not, the dist/caritat.js package is UMD, so should work in most any context you put it. It is heavily reliant on lodash, though, so make sure you've got that stowed away somewhere.

The code itself is written using ES2015 modules, and gets picked up that way by rollup if you want to bundle it. (Again, you'll need to figure out how to get lodash in there. I use babel-plugin-lodash.)

Wikipedia uses a fairly consistent example in its articles on voting systems, where a capital for Tennessee is being chosen. That example is constructed in such a way that the chief three single-winner methods give differing results: Plurality ("first past the post") selects Memphis, Instant runoff voting ("alternative vote") selects Knoxville, and Condorcet methods select Nashville.

So here's how to run these examples through caritat.

import {Election, irv, plurality, condorcet} from 'caritat';

var election = new Election({
  candidates: ['Chattanooga', 'Knoxville', 'Memphis', 'Nashville']
});

// Voters near Memphis.
election.addBallot(['Memphis', 'Nashville', 'Chattanooga', 'Knoxville'], 42);
// Voters near Nashville.
election.addBallot(['Nashville', 'Chattanooga', 'Knoxville', 'Memphis'], 26);
// Voters near Chattanooga.
election.addBallot(['Chattanooga', 'Knoxville', 'Nashville', 'Memphis'], 15);
// Voters near Knoxville.
election.addBallot(['Knoxville', 'Chattanooga', 'Nashville', 'Memphis'], 17);

var pluralityWinner = plurality(election); // Will return Memphis.
var irvWinner = irv(election); // Will return Knoxville.
var condorcetWinner = condorcet.winner(election); // Will return Nashville.

All of this is written by an inexperienced programmer who has way too much interest in the different counting systems, partly as a hobby project and partly for production use for a political party. (I didn't say I had a sane plan.)

There's a highly understandable convention of liberal licencing for JavaScript code. Most people going for liberal go for short and concise statements of intent. Me, I choose CC0. (That actually is short and concise, as lawyer-vetted licences go.) The short version is: I don't care. As far as I'm concerned, this is public domain. Do whatever. (The code is probably crap anyway.)