在 jCarouselLite 无缝滚动插件中，看到的如下定义，但是没有看懂，谁能解释下，谢谢.
// JavaScript Document
(function($){
$.fn.jCarouselLite=function(o){
o=$.extend({
maxSize:null,btnPrev:null,btnNext:null,btnGo:null,mouseWheel:false,auto:null,speed:200,easing:null,vertical:false,circular:true,visible:3,start:0,scroll:1,beforeStart:null,afterEnd:null
}
,o||{});
return this.each(function(){
var b=false,animCss=o.vertical?"top":"left",sizeCss=o.vertical?"height":"width";
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
就是下面这行代码
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
var c=$(this),ul=$("ul",c),tLi=$("li",ul),tl=tLi.size(),v=o.visible;
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
没有看懂这个变量 ul=$("ul",c)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
if(o.circular){
ul.prepend(tLi.slice(tl-v-1+1).clone()).append(tLi.slice(0,v).clone());
o.start+=v
}
var f=$("li",ul),itemLength=f.size(),curr=o.start;
c.css("visibility","visible");
f.css({
overflow:"hidden",float:o.vertical?"none":"left"
});
ul.css({
margin:"0",padding:"0",position:"relative","list-style-type":"none","z-index":"1"
});
c.css({
overflow:"hidden",position:"relative","z-index":"2",left:"0px"
});
var g=o.vertical?height(f):width(f);
var h=g*itemLength;
var j=g*v;
if(o.maxSize != null) j = j> o.maxSize?o.maxSize:j;
f.css({
width:f.width(),height:f.height()
});
ul.css(sizeCss,h+"px").css(animCss,-(curr*g));
c.css(sizeCss,j+"px");
if(o.btnPrev)$(o.btnPrev).click(function(){
return go(curr-o.scroll)
});
if(o.btnNext)$(o.btnNext).click(function(){
return go(curr+o.scroll)
});
if(o.btnGo)$.each(o.btnGo,function(i,a){
$(a).click(function(){
return go(o.circular?o.visible+i:i)
})
});
if(o.mouseWheel&&c.mousewheel)c.mousewheel(function(e,d){
return d>0?go(curr-o.scroll):go(curr+o.scroll)
});
if(o.auto)setInterval(function(){
go(curr+o.scroll)
}
,o.auto+o.speed);
function vis(){
return f.slice(curr).slice(0,v)
};
function go(a){
if(!b){
if(o.beforeStart)o.beforeStart.call(this,vis());
if(o.circular){
if(a<=o.start-v-1){
ul.css(animCss,-((itemLength-(v*2))*g)+"px");
curr=a==o.start-v-1?itemLength-(v*2)-1:itemLength-(v*2)-o.scroll
}
else if(a>=itemLength-v+1){
ul.css(animCss,-((v)*g)+"px");
curr=a==itemLength-v+1?v+1:v+o.scroll
}
else curr=a
}
else{
if(a<0||a>itemLength-v)return;
else curr=a
}
b=true;
ul.animate(animCss=="left"?{
left:-(curr*g)
}
:{
top:-(curr*g)
}
,o.speed,o.easing,function(){
if(o.afterEnd)o.afterEnd.call(this,vis());
b=false
});
if(!o.circular){
$(o.btnPrev+","+o.btnNext).removeClass("disabled");
$((curr-o.scroll<0&&o.btnPrev)||(curr+o.scroll>itemLength-v&&o.btnNext)||[]).addClass("disabled")
}
}
return false
}
})
};
function css(a,b){
return parseInt($.css(a[0],b))||0
};
function width(a){