问在JS中简化精灵动画

EN

var theSprite= $('.sprite');
var timesRun = 0;
var shift = 0;
var fps = 20;        

var anim = function() {

    setTimeout(function() {

        shift -= 520;
        theSprite.css('background-position', shift +'px 0');

        timesRun += 1;

        if(timesRun === 19) {
            timesRun = 0;
            shift = 0;
        }


        animAgain = requestAnimationFrame(anim);

    }, 1000 / fps);
}

anim();