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> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <h1>请往下滑</h1> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /><br /> <br /> <br /> <br /> <br /><br /> <br /> <br /> <br /> <br /><br /> <br /> <br /> <br /> <br /><br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /><> <div id="flypig"> <img src="http://www.jb51.netwp-content/themes/Jakesoft/images/flypig.gif"> </div> <div id="go">返回顶部</div></html>
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