moroshko / elo.js

Minimalistic Javascript implementation of a Elo rating system

Overview

Minimalistic Javascript implementation of a Elo rating system. K-factor of 32 is used.

How to use

1. Include elo.js
2. Use Elo.getNewRating() to calculate the new rating, or Elo.getRatingDelta() to calculate the delta.

Methods

getNewRating(myRating, opponentRating, myGameResult)

Calculates my new rating given the following parameters:

• myRating (number) - My rating before the game, e.g. 1600
• opponentRating (number) - Opponent's rating before the game, e.g. 1700
• myGameResult (number) - The result of the game, 1 if I won, 0 if I lost, or 0.5 if draw

Example

Elo.getNewRating(1600, 1700, 1)     // => 1620
Elo.getNewRating(1600, 1700, 0.5)   // => 1604
Elo.getNewRating(1600, 1700, 0)     // => 1588

getRatingDelta(myRating, opponentRating, myGameResult)

Calculates my new rating given the following parameters:

• myRating (number) - My rating before the game, e.g. 1600
• opponentRating (number) - Opponent's rating before the game, e.g. 1700
• myGameResult (number) - The result of the game, 1 if I won, 0 if I lost, or 0.5 if draw

Example

Elo.getRatingDelta(1600, 1700, 1)     // => 20
Elo.getRatingDelta(1600, 1700, 0.5)   // => 4
Elo.getRatingDelta(1600, 1700, 0)     // => -12