elo.js

function adjust(ratings) {
      ratings[0] = ratings[0] ? parseFloat(ratings[0]) : 1000;
      ratings[1] = ratings[1] ? parseFloat(ratings[1]) : 1000;
      var winnerExpected = 1 / (1 + (Math.pow(10,(ratings[1] - ratings[0]) / 400)));
      var loserExpected = 1 / (1 + (Math.pow(10,(ratings[0] - ratings[1]) / 400)));
      var k = 30;
      var winnerAdjustment = Math.round(ratings[0] + (k * (1 - winnerExpected)));
      var loserAdjustment = Math.round(ratings[1] + (k * (0 - loserExpected)));
      return [winnerAdjustment, loserAdjustment];
}