js元素闪动效果

<img src="http://yjy.allbring.com/UpLoadFiles/head/p1_20140326104945_17-10164142709.jpg"  style=" position:relative;"  id="aa" />

function setAnimation() {
             var attr = ["top", "left"], b = 0;
             u = setInterval(function () {
                 document.getElementById("aa").style[attr[b % 2]] = (b++) % 4 < 2 ? 0 : 4;
                 //alert(document.getElementById("aa").tagName); b++;
                 if (b > 30) {
                     clearInterval(u); b = 0;
                     setAnimation();
                 }
             }, 32);
}