ELO Points

script.js

// Calculates the log base 'base' of 'value' e.g. logBase(2, 4) is log_2 (4) = 2
function logBase(base, value) {
	return log(value)/log(base);
}

/*
 * Calculates the points earned after winning a match based on the following:
 * Min and max points: The minimum and maximum amount of points to be applied
 * Min and max delta: At what rank difference the min or max points should be applied (e.g. -500 and 500 ranking point difference)
 * Delta: How much ranking point difference there is between the two players (winningPlayer - losingPlayer)
 * 
 * This is an exponential function, so the following apply: minPoints, maxDelta - minDelta
 * and minPoints - minDelta must not be zero, otherwise the universe implodes. Simple, right?
 *
 * When calculating how many points are won when player wins, an example is as follows:
 * winningPlayerPoints += calculatePoints(1, 100, -500, 500, 200);
 *
 * When calculating how many points are lost when player loses, flip function along y-axis i.e. 1/calculatePoints
 * e.g. losingPlayerPoints -= 1/calculatePoints(1, 100, -500, 500, -100);
 */
function calculatePoints(minPoints, maxPoints, minDelta, maxDelta, delta) {
	// If the difference in ranking is less than the minimum specified delta, return the minPoints
	if (delta < minDelta) {
		return minPoints;
	}
	
	// If the difference in ranking is greater than the maximum specified delta, return the maxPoints
	if (delta > maxDelta) {
		return maxPoints;
	}
	
	// Delta is in between min and max delta, calculate amount of points won
	let a = logBase(maxDelta-minDelta, maxPoints/minPoints);
	let b = logBase(a, minPoints - minDelta);
	
	// Return result of exponential function
	return Math.pow(a, delta+b);
}