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();