<script type="text/javascript">
        //实例化animationHover对象
        window.onload = function(){
            var ah = new animationHover(); 
            ah.init();
        };
        //初始化标签对象
        function animationHover(){
            this.step = document.getElementById('step');
            this.stepLi = this.step.getElementsByTagName('li');
            this.line = document.getElementById('line');
            this.attr = null;
            this.timer = null;
            this.target = null;
                            
            }
        //初始化事件
        animationHover.prototype.init=function(){
            This =this;
            for(var i=0;i<this.stepLi.length;i++){
                this.stepLi[i].index=i;
                //给li标签绑定事件
                this.stepLi[i].onmouseover=function(e){   
                    var myIndex=this.index;
                    This.onOver(This.line,(myIndex*162+55));
                    };
                this.stepLi[i].onmouseout=function(){           
                   This.line.style.left=myIndex*162+55+'px';
                    };   
                
                }
            };
        //定义鼠标经过的处理函数
        animationHover.prototype.onOver=function(obj,target){
            This=this;
            clearInterval(this.timer);
            This.target=target;
            timer=setInterval(function(){
                var target=This.target; //停止的目标点
                var attrValue=parseInt(This.getStyle(obj,'left'));
                var dx=target-attrValue; //距目标点的"路程"
                var speed=1/10*dx;
                speed=speed>0?Math.ceil(speed):Math.floor(speed);
                            //防止取整引起的抖动
                if(target==attrValue) clearInterval(timer);
                            //如果到达目标点，关闭定时器
                else{
                    obj.style.left=attrValue+speed+'px';
                }
                },100);
                                    
            };
        //获取当前标签对象的css属性值
        animationHover.prototype.getStyle =function(obj,attr){                    
            if(obj.currentStyle){               
                return obj.currentStyle[attr];
            }else{
                return getComputedStyle(obj,false)[attr];
            }
            };   
</script>