determine how far from the centre an index is given that the array has been rotated an unknown amount and we know the middleIndex

gistfile1.js

displacementFromMiddle = function(index, arraySize, middleIndex) {
        if (index == middleIndex) return 0;
    
        var imagesRadius = Math.floor(arraySize / 2)

        var x = index - middleIndex;
        var y;

        if (x > imagesRadius) {
        	y = x - arraySize;
        }
        else if (x < -imagesRadius) {
        	y = x + arraySize
        }
        else {
        	y = x; 
        }

        return y;
    }


var result = displacementFromMiddle(2, 5, 0)
var result = displacementFromMiddle(3, 5, 0)
var result = displacementFromMiddle(4, 5, 0)
var result = displacementFromMiddle(5, 5, 0)