var babyzone = function() {
	function id(name) {return document.getelementbyid(name);}
	//遍历函数
	function each(arr, callback) {
		if (arr.foreach) {arr.foreach(callback);} 
		else { for (var i = 0, len = arr.length; i < len; i++) callback.call(this, arr[i], i, arr);}
	}
	function fadein(elem) {
		setopacity(elem, 0)
		for ( var i = 0; i < 20; i++) {
			(function() {
				var pos = i * 5;
				settimeout(function() {
					setopacity(elem, pos)
				}, i * 25);
			})(i);
		}
	}
	function fadeout(elem) {
		for ( var i = 0; i <= 20; i++) {
			(function() {
				var pos = 100 - i * 5;
				settimeout(function() {
					setopacity(elem, pos)
				}, i * 25);
			})(i);
		}
	}
	// 设置透明度
	function setopacity(elem, level) {
		if (elem.filters) {
			elem.style.filter = "alpha(opacity=" + level + ")";
		} else {
			elem.style.opacity = level / 100;
		}
	}
	return {
		//count:图片数量，wrapid:包裹图片的div,ulid:按钮div,	infoid：信息栏
		scroll : function(count,wrapid,ulid,infoid) {
			var self=this;
			var targetidx=0;      //目标图片序号
			var curindex=0;       //现在图片序号
			//添加li按钮
			var frag=document.createdocumentfragment();
			this.num=[];    //存储各个li的应用，为下面的添加事件做准备
			this.info=id(infoid);
			for(var i=0;i<count;i++){
				(this.num[i]=frag.appendchild(document.createelement("li"))).innerhtml=i+1;
			}
			id(ulid).appendchild(frag);
			
			//初始化信息
			this.img = id(wrapid).getelementsbytagname("a");
			this.info.innerhtml=self.img[0].firstchild.title;
			//this.num[0].classname="on";
			//将除了第一张外的所有图片设置为透明
			each(this.img,function(elem,idx,arr){
				if (idx!=0) setopacity(elem,0);
			});
			
			//为所有的li添加点击事件
			each(this.num,function(elem,idx,arr){
				elem.onclick=function(){
					self.fade(idx,curindex);
					curindex=idx;
					targetidx=idx;
				}
			});
			
			//自动轮播效果
			var itv=setinterval(function(){
				if(targetidx<self.num.length-1){
					targetidx++;
				}else{
					targetidx=0;
					}
				self.fade(targetidx,curindex);
				curindex=targetidx;
				},4000);
			id(ulid).onmouseover=function(){clearinterval(itv)};
			id(ulid).onmouseout=function(){
				itv=setinterval(function(){
					if(targetidx<self.num.length-1){
						targetidx++;
					}else{
						targetidx=0;
						}
					self.fade(targetidx,curindex);
					curindex=targetidx;
				},4000);
			}
		},
		fade:function(idx,lastidx){
			if(idx==lastidx) return;
			var self=this;
			fadeout(self.img[lastidx]);
			fadein(self.img[idx]);
			each(self.num,function(elem,elemidx,arr){
				if (elemidx!=idx) {
					self.num[elemidx].classname="";
				}else{
					self.num[elemidx].classname="on";
					}
			});
			this.info.innerhtml=self.img[idx].firstchild.title;
		}
	}
}();