Jquery滚动插件–Xslider：支持水平滚动和垂直滚动的多种效果

源地址 http://www.rjboy.cn/?p=708

本插件在原有基础上，添加了一些小功能：

1.点击单个unit时，自动使该unit的左边或者右边unit显示出来。

/*
	http://www.rjboy.cn
	By sean during 2010.07 - 2010.12;
	
	Demo:
	$(".productshow").Xslider({//.productshow是要移动对象的外框,页面上所有绑定了类.productshow的对象都会有切换效果;
		unitdisplayed:3,//可视的单位个数   必需项;
		numtoMove:1,//要移动的单位个数    必需项;
		viewedSize:120,//可视宽度或高度     不传入则查找要移动对象外层的宽或高度;
		scrollobj:".vscrollobj",//要移动的对象    不传入则查找productshow下的ul;
		unitlen:20,//移动的单位宽或高度      不传入则查找li的尺寸;
		scrollobjSize:$(".vscrollobj").height(),//移动最长宽或高（要移动对象的宽度或高度）   不传入则由li个数乘以unitlen计算;
		dir:"V",//水平移动还是垂直移动       默认H为水平移动，传入V则表示垂直移动（注意是大写字母）;
		loop:"cycle",//循环滚动            不传入则不循环滚动;
		speed:500, //滚动速度      默认为500;
		autoscroll:2000//自动移动间隔时间（毫秒）     不传入则不会自动移动;
	});
*/

(function($){
	$.extend($.easing,{
		easeInSine: function (x, t, b, c, d) {
			return -c * Math.cos(t/d * (Math.PI/2)) + c + b;
		}
	});

	$.fn.Xslider=function(settings){
		settings=$.extend({},$.fn.Xslider.sn.defaults,settings);
		this.each(function(){
			var scrollobj=settings.scrollobj ? $(this).find(settings.scrollobj) : $(this).find("ul"),
			    viewedSize=settings.viewedSize || (settings.dir=="H" ? scrollobj.parent().width() : scrollobj.parent().height()),//length of the wrapper visible;
			    scrollunits=scrollobj.find("li"),//units to move;
			    unitlen=settings.unitlen || (settings.dir=="H" ? scrollunits.eq(0).outerWidth() : scrollunits.eq(0).outerHeight()),
			    unitdisplayed=settings.unitdisplayed,//units num displayed;
				numtoMove=settings.numtoMove > unitdisplayed ? unitdisplayed : settings.numtoMove,
			    scrollobjSize=settings.scrollobjSize || scrollunits.length*unitlen,//length of the scrollobj;
			    offset=0,//max width to move;
			    offsetnow=0,//scrollobj now offset;
			    movelength=unitlen*numtoMove,
				pos=settings.dir=="H" ? "left" : "top",
			    moving=false,//moving now?;
			    btnright=$(this).find("p.jtright"),
			    btnleft=$(this).find("p.jtleft");
			
				
			btnright.unbind("click");
			btnleft.unbind("click");
			
			// 重新计算
			scrollobjSize = 0;
			$.each(scrollunits, function(index, unit){
				scrollobjSize += $(unit).outerWidth();
				$(unit).bind("click", function(){
					// 将点击的unit的左边或者右边智能显示						
					if ($(this).position().left < (offsetnow + unitlen)){
						btnleft.click();
					}else if (($(this).position().left + $(unit).outerWidth() + unitlen) > (offsetnow+viewedSize) ){
						btnright.click();
					}
				});});
			
			settings.dir=="H" ? scrollobj.css("left","0px") : scrollobj.css("top","0px");
							
			if(scrollobjSize>viewedSize){
				if(settings.loop=="cycle"){
					btnleft.removeClass("jtgrayleft");
					if(scrollunits.length<2*numtoMove+unitdisplayed-numtoMove){
						scrollobj.find("li").clone().appendTo(scrollobj);	
					}
				}else{
					btnleft.addClass("jtgrayleft");
					offset=scrollobjSize-viewedSize;
				}
				btnright.removeClass("jtgrayright");
			}else{
				btnleft.addClass("jtgrayleft");
				btnright.addClass("jtgrayright");
			}

			btnleft.click(function(){
				if($(this).is("[class*='jtgrayleft']")){return false;}
				
				if(!moving){
					moving=true;
					
					if(settings.loop=="cycle"){
						scrollobj.find("li:gt("+(scrollunits.length-numtoMove-1)+")").prependTo(scrollobj);
						scrollobj.css(pos,"-"+movelength+"px");
						$.fn.Xslider.sn.animate(scrollobj,0,settings.dir,settings.speed,function(){moving=false;});
					}else{
						offsetnow-=movelength;
						if(offsetnow>unitlen*unitdisplayed-viewedSize){
							$.fn.Xslider.sn.animate(scrollobj,-offsetnow,settings.dir,settings.speed,function(){moving=false;});
						}else{
							$.fn.Xslider.sn.animate(scrollobj,0,settings.dir,settings.speed,function(){moving=false;});
							offsetnow=0;
							$(this).addClass("jtgrayleft");
						}
						btnright.removeClass("jtgrayright");
					}
				}

				return false;
			});
			btnright.click(function(){
				if($(this).is("[class*='jtgrayright']")){return false;}
				
				if(!moving){
					moving=true;
					
					if(settings.loop=="cycle"){
						var callback=function(){
							scrollobj.find("li:lt("+numtoMove+")").appendTo(scrollobj);
							scrollobj.css(pos,"0px");
							moving=false;
						};
						$.fn.Xslider.sn.animate(scrollobj,-movelength,settings.dir,settings.speed,callback);
					}else{
						offsetnow+=movelength;
						if(offsetnow