animate-sprite-loop.js

window.setInterval(function() {
    var position = element.css('background-position'),
        positionX = Math.abs($.nounit(position.split(' ')[0])),
        positionY = position.split(' ')[1],
        frameWidth = 66,
        numFrames = 8,
        currentFrame = Math.floor(positionX / frameWidth),
        nextFrame, nextFrameOffset;
    
    nextFrame = (currentFrame == (numFrames - 1)) ? 0 : currentFrame + 1;
    nextFrameOffset = nextFrame * frameWidth * -1;
    
    element.css('background-position', nextFrameOffset + 'px ' + positionY);
}, 100);