javascript中返回顶部按钮的实现

炫酷的返回顶部功能

js核心代码

window.onscroll = function(){
  var t = document.documentElement.scrollTop || document.body.scrollTop;
  var top_div = document.getElementById( "go" );
  if( t >= 300 ) {
    top_div.style.display = "block";
  } else {
    top_div.style.display = "none";
  }
} 

var ptt=20;
function pageScroll() {

document.getElementById('flypig').style.display='block';
window.scrollBy(0,-10); //每次上升10px

if(document.body.scrollTop==0) {
  document.getElementById('flypig').style.marginBottom=ptt+'px';
  ptt=ptt+10;
}
scrolldelay = setTimeout('pageScroll()',2); //2毫秒重复执行一次

if(ptt>=1000){
  ptt=0;
  document.getElementById('flypig').style.marginBottom=20+'px';
  document.getElementById('flypig').style.display='none';
  clearTimeout(scrolldelay);
}
//pageScroll ends
}

html

<!DOCTYPE html>
<html>
<head>
 <title>返回顶部按钮的实现</title>
 <meta charset="utf-8" />
<style>
body{
  margin:0px;
}
#flypig{
 display: none;
 float: left;
 position: fixed;
 bottom: 20px;
 margin-left: 75%;
 cursor: pointer;
 margin-bottom: 20px;
}
#go{
 display: block;
 float: left;
 position: fixed;
 bottom: 10px;
 margin-left: 75%;
 cursor: pointer;
}
</style>
<script>

window.onscroll = function(){
  var t = document.documentElement.scrollTop || document.body.scrollTop;
  var top_div = document.getElementById( "go" );
  if( t >= 300 ) {
    top_div.style.display = "block";
  } else {
    top_div.style.display = "none";
  }
} 

var ptt=20;
function pageScroll() {

document.getElementById('flypig').style.display='block';
window.scrollBy(0,-10); //每次上升10px

if(document.body.scrollTop==0) {
  document.getElementById('flypig').style.marginBottom=ptt+'px';
  ptt=ptt+10;
}
scrolldelay = setTimeout('pageScroll()',2); //2毫秒重复执行一次

if(ptt>=1000){
  ptt=0;
  document.getElementById('flypig').style.marginBottom=20+'px';
  document.getElementById('flypig').style.display='none';
  clearTimeout(scrolldelay);
}
//pageScroll ends
} 

</script>
</head>
<body>
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<h1 style="text-align:center;">请往下滑</h1>
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<br /><!--让你的页面足够的长-->
<div style="display: none; float: left; position: fixed; margin-left: 50%; cursor: pointer; margin-bottom: 20px;" id="flypig">
<img src="/wp-content/themes/Jakesoft/images/flypig.gif">    </div>
<div style="display: none; float: left; position: fixed; bottom: 10px; margin-left: 50%; cursor: pointer;" id="go" onclick="pageScroll()">返回顶部</div></html>

以上所述就是本文的全部内容了，希望大家能够喜欢。