function getByClass(a,b){

if(a.getElementsByClassName){

return a.getElementsByClassName(b);

}

var arr = [];

var all = a.getElementsByTagName('*');

var re = RegExp("\\b"+b+"\\b","g");

for (var i = 0; i < all.length; i++) {

if(re.test(all[i].className)){

arr.push(all[i]);

}

};

return arr;

};

window.onload = function(){

var aLi=document.getElementsByTagName('ul')[0].getElementsByTagName('li');

var aBtn=getByClass(document, 'foot')[0].getElementsByTagName('a');

var oCaret=getByClass(document, 'caret')[0];

var aPos=[];

var timer=null;

var i=0;

for(i=0;i<aLi.length;i++){

aLi[i].index=i;

aPos[i]=aLi[i].offsetLeft;

aLi[i].style.left=aPos[i]+'px';

}

for(i=0;i<aLi.length;i++){

aLi[i].style.position='absolute';

}

aBtn[0].onclick=function(){

var i=aLi.length-1;

clearTimeout(timer);

function next(){

if(i>=aLi.length/2){

move(aLi[i],{left:900})

timer = setTimeout(next, 100);

i--;

}else{

timer=setTimeout(next2, 150);

};

};

function next2(){

if(i>=0){

move(aLi[i],{left:aPos[i]});

timer=setTimeout(next2, 100);

}

i--;

};

next();

aBtn[1].className='';

this.className='show';

move(oCaret,{left:this.offsetLeft+this.offsetWidth/2});

};

aBtn[1].onclick=function(){

var i = 0;

clearTimeout(timer);

function next(){

if(i<aLi.length/2){

move(aLi[i],{left:-200})

timer = setTimeout(next, 100);

i++;

}else{

timer=setTimeout(next2, 150);

};

};

function next2(){

if(i<aLi.length){

move(aLi[i],{left:aPos[i-aLi.length/2]})

timer=setTimeout(next2, 100);

}

i++;

};

next();

aBtn[0].className='';

this.className='show';

move(oCaret,{left:this.offsetLeft+this.offsetWidth/2});

};

};