jquery 锚点链接平滑跳转实现回到顶部

$(document).ready(function(){
$(".gotop").anchorgowhere({target:1});
$(".godown").anchorgowhere({target:1});
$(".gonext").anchorgowhere({target:1});
$(".gofront").anchorgowhere({target:1});
$(".govertical").anchorgowhere({target:2});
});
 

<a href="#menu1" class="godown">菜单一</a>
<a href="#menu2" class="gonext">懒人们，点这里看第二章节</a>
<a href="#menu1" class="gofront">怎么了，前面一章忘记了？</a>
<a href="#right" class="govertical">还没看过瘾，我带你到右边去看看-&gt;</a>
<a href="#body" class="gotop">返回顶部</a></span>

jquery.fn.anchorgowhere = function(options){
var obj = jquery(this);
var defaults = {target:0, timer:1000};
var o = jquery.extend(defaults,options);
obj.each(function(i){
jquery(obj[i]).click(function(){
var _rel = jquery(this).attr("href").substr(1);
switch(o.target){
case 1:
 var _targettop = jquery("#"+_rel).offset().top;
 jquery("html,body").animate({scrolltop:_targettop},o.timer);
 break;
 case 2:
 var _targetleft = jquery("#"+_rel).offset().left;
 jquery("html,body").animate({scrollleft:_targetleft},o.timer);
 break;
 }
 return false;
 });
});
};