基于jquery的回到页面顶部按钮

.scroll-up {
background: #dcdcdc url(up.png) no-repeat center center;
width:48px !important; /*for ff and other standard browser*/
height:48px !important;
_width: 58px; /*for IE6 nonstandard box model*/
_height: 58px;
position: fixed;
_position: absolute; /*for IE6 fixed bug*/
opacity: .6;
filter: Alpha(opacity=60); /*for IE opacity*/
padding:5px;
cursor: pointer;
display: none;
/*css3 property for ff chrome*/
border-radius:5px;
-webkit-transition-property: background-color, opacity;
-webkit-transition-duration: 1s;
-webkit-transition-timing-function: ease;
-moz-transition-property: background-color;
-moz-transition-duration: 1s;
-moz-transition-timing-function: ease;
}
.scroll-up:hover {
background-color:#B9B9B9;
opacity: .8;
}

;(function($) {
$.scrollBtn = function(options) {
var opts = $.extend({}, $.scrollBtn.defaults, options);
var $scrollBtn = $(<DIV></DIV>).css({
bottom: opts.bottom + px,
right: opts.right + px
}).addClass(scroll-up).attr(title, opts.title)
.click(function() {
$(html, body).animate({scrollTop: 0}, opts.duration);
}).appendTo(body);
// 绑定到window的scroll事件
$(window).bind(scroll, function() {
var scrollTop = $(document).scrollTop(),
viewHeight = $(window).height();
// 小于配置的显示范围 则fadeOut
if(scrollTop <= opts.showScale) {
if($scrollBtn.is(:visible))
$scrollBtn.fadeOut(500);
// 大于配置的显示范围 则fadeIn
} else {
if($scrollBtn.is(:hidden))
$scrollBtn.fadeIn(500);
}
// 解决IE6下css中fixed没有效果的bug
if(isIE6()) {
var top = viewHeight + scrollTop - $scrollBtn.outerHeight() - opts.bottom;
$scrollBtn.css(top, top + px);
}
});
// 判断是否为IE6
function isIE6() {
if($.browser.msie) {
if($.browser.version == 6.0) return true;
}
}
};
/**
* -params
* -showScale: scroll down how much to show the scrollup button
* -right: to right of scrollable container
* -bottom: to bottom of scrollable container
*/
$.scrollBtn.defaults = { // 默认值
showScale: 100, // 超过100px 显示按钮
right:10,
bottom:10,
duration:200, // 回到页面顶部的时间间隔
title:back to top // div的title属性
}
})(jQuery);
$.scrollBtn({
showScale: 200, //下滚200px后 显示按钮
bottom:20, // 靠底部20px
right:20 // 靠右部20px
});