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带有动画返回顶部

2021-06-07 20:04:58 作者：互联网

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {
      padding: 0;
      margin: 0;
    }

    .w {
      width: 1200px;
      margin: 0 auto;
    }

    .header {
      height: 100px;
      background-color: salmon;
    }

    .main {
      margin-top: 20px;
      height: 1400px;
      background-color: seagreen;
    }

    .footer {
      margin-top: 20px;
      height: 200px;
      background-color: darkkhaki;
    }

    .aside {
      width: 50px;
      height: 200px;
      background-color: rgb(29, 22, 19);
      position: absolute;
      left: 50%;
      top: 300px;
      margin-left: 600px;
    }
  </style>
</head>

<body style="height: 2000px;">
  <div class="aside"></div>
  <div class="header w"></div>
  <div class="main w"></div>
  <div class="footer w"></div>
</body>
<script>
  var header = document.querySelector(".header");
  var aside = document.querySelector(".aside");
  var h = header.offsetHeight
  var tt = aside.offsetTop;
  var lossDistance = aside.offsetTop - h;
  document.addEventListener("scroll", function () {
    var pageY = window.pageYOffset;
    if (window.pageYOffset >= h) {
      aside.style.position = "fixed"
      aside.style.top = lossDistance + "px"
    } else {
      aside.style.position = "absolute"
      aside.style.top = tt + "px"
    }
  })

  aside.addEventListener("click", function () {

    var timer = setInterval(function () {
      var pageY = window.pageYOffset;
      var current = Math.ceil(pageY / 10)
      window.scrollTo(0, pageY - current);
      if (current == 0) {
        clearInterval(timer)
      }
    }, 15)
  })
</script>

</html>

标签：返回,动画,顶部,top,aside,height,header,var,margin
来源： https://www.cnblogs.com/fc11/p/14860286.html