function?animate(num){
????var?newLeft?=?parseInt(list.style.left)?+?num
????list.style.left?=?newLeft?+?'px';
????if(newLeft?>?0){
???????????list.style.left?=?-2400?+?'px';
????}else?if(newLeft?<?-2400){
???????????list.style.left?=?0;
???????????}
????}
????next.onclick?=?function(){
???????????animate(-num);
????}
????prev.onclick?=?function(){
???????????animate(num);
????}

????<div?id="list"?style="left:0px">
????????<img?src="img/1.jpg"?alt="pic">
????????<img?src="img/2.jpg"?alt="pic">
????????<img?src="img/3.jpg"?alt="pic">
????????<img?src="img/4.jpg"?alt="pic">
????????<img?src="img/5.jpg"?alt="pic">
????</div>

直接這樣貌似也可以啊，不用模擬第一個跟最后一個圖好像點起來也沒問題