gistfile1

function drawDashedLine(context, startPoint, endPoint)
{
    var axis = startPoint.x === endPoint.x ? 'y' : 'x',
        distance = endPoint[axis] - startPoint[axis],
        dashes = CEIL(distance / 4),
        index = 0,
        point = CGPointMakeCopy(startPoint),
        segments = [];

    for (; index < dashes; ++index)
    {
        segments.push(CGPointMakeCopy(point));
        point[axis] = MIN(point[axis] + 3.0, endPoint[axis]);
        segments.push(CGPointMakeCopy(point));
        point[axis] += 1.0;
    }

    CGContextStrokeLineSegments(context, segments);
}