jqery实现返回顶部效果

jqery实现返回顶部效果，过渡性
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title></title>
    <style>
        /*CSS源代码*/
        body{
            background:#fff;
            height: 2000px;
        }

        #gotoTop{
            position:fixed;
            right:50px;
            bottom:50px;
            z-index:7;
            display: none;
            visibility:hidden;
            width:26px;
            height:48px;
            background:url("01.jpg") no-repeat 50% 0;
            opacity:0;
            -webkit-transition:visibility .6s cubic-bezier(0.6,0.04,0.98,0.335),opacity .6s cubic-bezier(0.6,0.04,0.98,0.335),-webkit-transform .6s cubic-bezier(0.6,0.04,0.98,0.335);
            -moz-transition:visibility .6s cubic-bezier(0.6,0.04,0.98,0.335),opacity .6s cubic-bezier(0.6,0.04,0.98,0.335),-moz-transform .6s cubic-bezier(0.6,0.04,0.98,0.335);
            transition:visibility .6s cubic-bezier(0.6,0.04,0.98,0.335),opacity .6s cubic-bezier(0.6,0.04,0.98,0.335),transform .6s cubic-bezier(0.6,0.04,0.98,0.335);
        }
        #gotoTop i {
            display:block;
            margin-top:48px;
            height:14px;
            background:url("01.jpg") no-repeat 50% -48px;
            opacity:.5;
            -webkit-transition:-webkit-transform .2s;
            -moz-transition:-moz-transform .2s;
            transition:transform .2s;
            -webkit-transform-origin:50% 0;
            -moz-transform-origin:50% 0;
            transform-origin:50% 0
        }
        #gotoTop:hover {
            background-position:50% -62px
        }
        #gotoTop:hover i {
            background-position:50% 100%;
            -webkit-animation:flaming .7s infinite;
            -moz-animation:flaming .7s infinite;
            animation:flaming .7s infinite
        }
        #gotoTop.show {
            visibility:visible;
            opacity:1
        }
        #gotoTop.launch {
            background-position:50% -62px;
            opacity:0;
            -webkit-transform:translateY(-800px);
            -moz-transform:translateY(-800px);
            -ms-transform:translateY(-800px);
            transform:translateY(-800px);
            pointer-events:none;
        }
        #gotoTop.launch i {
            background-position:50% 100%;
            -webkit-transform:scale(1.4,3.2);
            -moz-transform:scale(1.4,3.2);
            transform:scale(1.4,3.2)
        }

        @-webkit-keyframes flaming {
            from,to {
                opacity:.5
            }
            50% {
                opacity:.9;
                -webkit-transform:scale(1.1,1.3)
            }
        }@-moz-keyframes flaming {
             from,to {
                 opacity:.5
             }
             50% {
                 opacity:.9;
                 -moz-transform:scale(1.1,1.3)
             }
         }@keyframes flaming {
              from,to {
                  opacity:.5
              }
              50% {
                  opacity:.9;
                  transform:scale(1.1,1.3)
              }
          }
    </style>
</head>
<body>
<!-- HTML代码片段中请勿添加<body>标签 //-->

<a id="gotoTop"><i></i></a>




<!-- 推荐开源CDN来选取需引用的外部JS //-->
<script type="text/javascript" src="http://cdn.gbtags.com/jquery/1.11.1/jquery.min.js"></script>

<script>
    /*Javascript代码片段*/
    $(document).ready(function(){
        var el = $("#gotoTop");
        el.on("click",function(){
            $(this).addClass("launch");
            $("body,html").animate({scrollTop:0},800);
        });
        $(window).scroll(function(){
            var scroll =  $(window).scrollTop();
            if(scroll == 0){
                el.removeClass("launch");
            }
            if( scroll >= 300 ){
                el.show().addClass("show").removeClass("hide");
            }else{
                el.fadeOut().addClass("hide").removeClass("show");
            }
        });
    });
</script>
</body>
</html>
jqery实现返回顶部效果

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