JS缓冲运动案例：右侧居中悬浮窗

<!DOCTYPE html>
<html lang="zh-CN">

<head>
  <meta charset="UTF-8">
  <title>JS小案例：右侧缓冲悬浮框</title>
  <style>
    body {
      height: 2000px;
      margin: 0px;
    }

    #div1 {
       100px;
      height: 150px;
      background: red;
      position: absolute;
      right: 0;
      bottom:calc(50% - 75px);
    }
  </style>
  <script>
//补充代码

  </script>
</head>

<body>
  <div id='div1'></div>
</body>

</html>

参考案例

<!DOCTYPE html>
<html lang="zh-CN">

<head>
  <meta charset="UTF-8">
  <title>JS小案例：右侧缓冲悬浮框</title>
  <style>
    body {
      height: 2000px;
      margin: 0px;
    }

    #div1 {
       100px;
      height: 150px;
      background: red;
      position: absolute;
      right: 0;
      bottom:calc(50% - 75px);
    }
  </style>
  <script>

    window.onscroll = function () {
      startMove();
    }

    var timer = null;

    function startMove() {

      var oDiv = document.getElementById('div1');

      clearInterval(timer);

      timer = setInterval(function () {

        var scrollTop = document.documentElement.scrollTop || document.body.scrollTop;

        var iTarget = (document.documentElement.clientHeight - oDiv.offsetHeight) / 2 + scrollTop;
        iTarget = Math.ceil(iTarget);
        var speed = (iTarget - oDiv.offsetTop) / 4;

        speed = speed > 0 ? Math.ceil(speed) : Math.floor(speed);

        if (oDiv.offsetTop == iTarget) {

          clearInterval(timer);

        } else {

          oDiv.style.top = oDiv.offsetTop + speed + 'px';

        }

      }, 30)

    }

  </script>
</head>

<body>
  <div id='div1'></div>
</body>

</html>