JavaScript使用setTimeout实现轮循动画

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
</head>
<body>
  <div id='box'></div>
  <script>
    var oBox = document.getElementById("box");
    var maxLeft = utils.win('clientWidth')-oBox.offsetWidth;
    var step = 5;
    var timer = null;
    //使用递归思想完成setTimeout的轮循动画：每一次在执行动画之前把上一次设置没用的定时器清除掉，节约我们的内存空间
    function move(){
      window.clearTimeout(timer);
      var curLeft = utils.css(oBox,"left");
      if(curLeft+step >= maxLeft){//边界判断
        utils.css(oBox,"left",maxLeft);
        return;
      }
      curLeft+=step;
      utils.css(oBox,"left",curLeft);
      timer = window.setTimeout(move,10)
    }
    move();

  </script>
</body>
</html>