图片轮播页面被切换，一段时间再回到轮播页面，轮播为啥会混乱？

Question

图片轮播页面被切换，一段时间再回到轮播页面，轮播为啥会混乱？

我写的是

var index = 1;

var animated = false;

function animate(offset){

animated = true;

index+=1;

var newLeft = parseInt(rolling.style.left)+offset;

var time = 300;

var interval = 10;

var speed = offset/(time/interval);

function go(){

if(speed<0 && parseInt(rolling.style.left)>newLeft){

rolling.style.left = parseInt(rolling.style.left) + speed +'px';

setTimeout(go,interval);

}else{

animated = false;

rolling.style.left = newLeft +'px';

if(newLeft<-7612){

rolling.style.left = -1903 + 'px';

}

if(index>4){

index = 1;

showButton();

}

}

}

go();

}

var timer;

function play(){

timer = setInterval(function(){

animate(-1903);

showButton();

console.log(index);

},3000)

}

play();