实现功能如下：
1. 二维码展示功能；
2. “回到顶部”功能。(选择“全屏预览”，滑动滚动条，查看回到顶部功能)
效果图：
图(1) 初始效果
图(2) 鼠标悬浮效果
实例代码：
<!doctype html> <html lang="zh-CN"> <head> <meta charset="utf-8" /> <title>工具条</title> <script type="text/javascript" src="https://code.jquery.com/jquery-3.1.1.min.js"></script> <style type="text/css"> body{ background-color:#69C; } .toolbar{ position:fixed; left:50%; bottom:5px; margin-left:-26px; } .toolbar-item{ position:relative; display:block; width:52px; height:52px; background-image:url(); background-repeat:no-repeat; margin-top:1px; -webkit-transition:background-position 1s; -moz-transition:background-position 1s; -ms-transition:background-position 1s; -o-transition:background-position 1s; transition:background-position 1s; } .toolbar-item-wenxin{ background-position:0 -798px; } .toolbar-item-wenxin:hover{ background-position:0 -860px; } .toolbar-item-feedback{ background-position:0 -426px; } .toolbar-item-feedback:hover{ background-position:0 -488px; } .toolbar-item-app{ background-position:0 -550px; } .toolbar-item-app:hover{ background-position:0 -612px; } .toolbar-item-top{ background-position:0 -674px; } .toolbar-item-top:hover{ background-position:0 -736px; } .toolbar-layer{ position:absolute; right:46px; bottom:-10px; width:172px; background-image:url(); background-repeat:no-repeat; opacity:0; filter:alpha(opacity=0); -webkit-transform-origin:95% 95%; -moz-transition-origin:95% 95%; -ms-transition-origin:95% 95%; -o-transition-origin:95% 95%; transform-origin:95% 95%; -webkit-transition:scale(0.01); -moz-transition:scale(0.01); -ms-transition:scale(0.01); -o-transition:scale(0.01); transform:scale(0.01); -webkit-transition:all 1s; -moz-transition:all 1s; -ms-transition:all 1s; -o-transition:all 1s; transition:all 1s; } .toolbar-item-wenxin .toolbar-layer{ height:212px; background-position:0 0; } .toolbar-item-app .toolbar-layer{ height:194px; background-position:0 -222px; } .toolbar-item:hover .toolbar-layer{ opacity:1; filter:alpha(opacity=100); -webkit-transition:scale(1); -moz-transition:scale(1); -ms-transition:scale(1); -o-transition:scale(1); transform:scale(1); } </style> <script type="text/javascript"> $(window).on('load',function(){ $('#backTop').on('click',go); $(window).on('scroll',function(){ checkPosition($(window).height()); }); checkPosition($(window).height());//防止刚开始刷新页面，返回顶部没有隐藏的问题，先让它执行一次，使其fadeOut }) //到达顶部 function go(){ $('html,body').scrollTop(0); } //检测位置 function checkPosition(pos){ if($(window).scrollTop() > pos){ $('#backTop').fadeIn();//滚动超过一个屏的宽度，就显示 }else{ $('#backTop').fadeOut(); } } </script> </head> <body> <div> <a href="javascript:;"> <span></span> </a> <a href="javascript:;"></a> <a href="javascript:;"> <span></span> </a> <a href="javascript:;"> </a> </div> <!--出现滚动条--> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> <p>1</p> </body> </html>