W3School TIY 亲自试一试！

<!DOCTYPE html>
<html>
<head>
<style> 
#myDIV {
  margin: 25px;
  width: 550px;
  height: 100px;
  background: orange;
  position: relative;
  font-size: 20px;
  text-align: center;
  -webkit-animation: mymove 4s infinite; /* Chrome, Safari, Opera */
  animation: mymove 4s infinite;
}

/* Chrome, Safari, Opera */
@-webkit-keyframes mymove {
  from {top: 0px;}
  to {top: 200px;}
}

@keyframes mymove {
  from {top: 0px;}
  to {top: 200px;}
}
</style>
</head>
<body>

<p>本例使用 addEventListener() 方法将 "animationstart" 和 "animationiteration" 事件附加到 DIV 元素。</p>

<p>当动画重复时，DIV 的背景颜色会是淡蓝色。</p>

<p>在本例中，elapsedTime 属性返回<b>重复动画</b>已运行的秒数：</p>

<p><b>注释：</b>IE9 及更早版本不支持 elapsedTime 属性。</p>

<div id="myDIV">动画开始了</div>

// 针对 Chrome、Safari 和 Opera 的代码
x.addEventListener("webkitAnimationIteration", myRepeatFunction);

// 标准语法
x.addEventListener("animationiteration", myRepeatFunction);

function myRepeatFunction(event) {
  this.style.backgroundColor = "lightblue";
  this.innerHTML = "Elapsed time: " + event.elapsedTime + " seconds";
}
</script>

</body>
</html>

W3School TIY Editor