text: 	function sNav(NavClass){
  		var _this=this;
  		//获得所有sNav
  		var oNav=_this.getByClass(document,NavClass)[0];
  		var aItem=oNav.getElementsByTagName('li');
  		this.aHoverItem=[];
  		this.aA=oNav.getElementsByTagName('a');
  		for (var i =0; i < aItem.length; i++) {
  			//获取原Item样式
  			var itemWidth=aItem[i].offsetWidth;
  			var itemHeight=oNav.offsetHeight;
  						
  			var oHoverItem=document.createElement('span');
  			this.aHoverItem.push(oHoverItem);
  		
  			//创建滑动容器并设置好位置
  			var itemWrap=document.createElement('div');
  			this.aA[i].appendChild(itemWrap);
  			itemWrap.appendChild(oHoverItem);
  			itemWrap.appendChild(aItem[i]);
  
  			//布局转换
  			itemWrap.style.position='absolute';
  			itemWrap.style.background='yellow';
  			//最外层容器占位
  			this.aA[i].style.width=itemWidth+'px';
  			this.aA[i].style.height=itemHeight+'px';
  			//设置itemWrap的Top值
  			itemWrap.style.top=-itemHeight+'px';
  			//传递参数-滑动距离
  			itemWrap.slideHeight=itemHeight;
  			//设置item样式
  			aItem[i].style.padding='0';
  			aItem[i].style.lineHeight=itemHeight+'px';
  			//设置oHoverItem样式
  			oHoverItem.style.height=itemHeight+'px';
  			oHoverItem.style.width=itemWidth+'px';
  			oHoverItem.style.display='block';
  			oHoverItem.style.lineHeight=itemHeight+'px';
  			oHoverItem.innerHTML=this.hoverText?this.hoverText:aItem[i].innerHTML;
  
  			//绑定事件
  			function eventRegister(itemWrap){
  				_this.myAddEvent(itemWrap,'mouseover',function(ev){
  					_this.hoverIn(ev,itemWrap);
  				});
  				_this.myAddEvent(itemWrap,'mouseout',function(ev){
  					_this.hoverOut(ev,itemWrap);
  				});
  			}
  			eventRegister(itemWrap);
  			
  		}	
  		//默认参数设置
  		this.slideSpeed=8;
  	}
  	
  	sNav.prototype.setText=function(json){
  		//设置hoverItem内容
  		for (var i in json) {
  			this.aHoverItem[i].innerHTML=json[i];
  		};
  	}
  
  	sNav.prototype.hoverIn=function(ev,itemWrap){
  		this.startMove(itemWrap,{'top':0});
  	}
  
  	sNav.prototype.hoverOut=function(ev,itemWrap){
  		this.startMove(itemWrap,{'top':-itemWrap.slideHeight});
  	}
  
  	 sNav.prototype.startMove=function(obj,json,fn){
  		var nowAttr;
  		var speed;
  		var k=this.slideSpeed;
  		var delay=20;
  		var _this=this;
  		clearInterval(obj.moveTimer);
  		obj.moveTimer=setInterval(function(){
  			var stop=true;
  			for(var attr in json){
  				var gotStyle=_this.getStyle(obj,attr);
  				var target=json[attr];
  				nowAttr=parseInt(gotStyle, 10);
  				if(nowAttr!=target){
  					stop=false;
  				}
  				if(stop){
  					clearInterval(obj.moveTimer);
  					fn&&fn(); 
  				}else{
  					speed=(target-nowAttr)/k;
  					speed=target>nowAttr?Math.ceil(speed):Math.floor(speed);
  
  					obj.style[attr]=(nowAttr+speed)+"px";
  				}
  			}	
  		}, delay);
  	}
  
  	 sNav.prototype.myAddEvent=function(obj,evName,fn){
  		if (obj.attachEvent){//IE
  			obj.attachEvent('on'+evName,function(){
  				fn.call(this);//避免this被修改
  			});
  		}else{
  			obj.addEventListener(evName, fn , false);
  		}
  	}
  	sNav.prototype.getByClass=function(oParent,className){
  		var aResult=[];
  		var arr=oParent.getElementsByTagName('*');
  		var re=new RegExp('\\b'+className+'\\b',i);
  
  		for (var i = 0; i < arr.length; i++) {
  			if(re.test(arr[i].className)){
  				aResult.push(arr[i]);
  			}
  		};
  		return aResult;
  	}
  	sNav.prototype.getStyle=function(obj,attr){
  		var value;
  		if(window.getComputedStyle){//IE
  			value = getComputedStyle(obj,false)[attr];
  		}else{
  			value = obj.currentStyle[attr];
  		}
  		value=parseInt(value,10);
  		return value;
  	}