<div id="container">
 <div id="list" style="left: -600px;">
 <img src="../image/1.jpg" alt="5">
 <img src="../image/1.jpg" alt="1">
 <img src="../image/2.jpg" alt="2">
 <img src="../image/3.jpg" alt="3">
 <img src="../image/4.jpg" alt="4">
 <img src="../image/5.jpg" alt="5">
 <img src="../image/1.jpg" alt="1">
 </div>
 <div id="buttons">
 <span class="on"></span>
 <span></span>
 <span></span>
 <span></span>
 <span></span>
 </div>
 <a href="javascript:;" id="prev" class="arrow"><</a>
 <a href="javascript:;" id="next" class="arrow">></a>
 </div>

window.onload = function(){
 //獲取元素
 var container = document.getElementById('container');
 var list = this.document.getElementById('list');
 var buttons = document.getElementById('buttons').getElementsByTagName('span');
 var prev = document.getElementById('prev');
 var next = document.getElementById('next');
 var index = 1;//默認(rèn)第一個(gè)小圓點(diǎn)亮

 //小圓點(diǎn)的點(diǎn)亮
 function showButton() {
 //遍歷小圓點(diǎn)的個(gè)數(shù)，當(dāng)觸發(fā)onclick事件后，className為‘on'的變?yōu)椤?。
 for(var i = 0;i < buttons.length; i++){
 if(buttons[i].className == 'on'){
 buttons[i].className = '';
 break;
 }
 }
 buttons[index - 1].className = 'on'; //原始第一個(gè)小圓點(diǎn)點(diǎn)亮，onclick事件觸發(fā)后，index+1
 }

 function animate (offset) {
 //獲取從第一張圖片開(kāi)始發(fā)生的偏移量
 var newLift = parseInt(list.style.left) + offset; 
 list.style.left = newLift + 'px';
 if(newLift > -600){ 
 //如果偏移量的位置大于-600的時(shí)候，圖片跳轉(zhuǎn)到第五張圖片
 list.style.left = -3000 + 'px';
 }
 if(newLift < -3000){ 
 //如果偏移量的位置大于-3000的時(shí)候，圖片跳轉(zhuǎn)到第一張圖片
 list.style.left = -600 + 'px';
 }
 }
 next.onclick = function () {
 //如果button的index為5的時(shí)候，再點(diǎn)擊next按鈕會(huì)返回 1；
 if(index == 5){
 index = 1;
 }else{
 index += 1;
 }
 showButton();
 animate(-600);
 }
 prev.onclick = function () {
 if(index == 1){
 index = 5;
 }else{
 index -= 1;
 }
 showButton();
 animate(600);
 }
}