JavaScript 实现简易图片自动轮播功能

<!doctype html>
<html>
 <head>
 <meta charset="utf-8" />
 <title>自动播放选项卡</title>
 <style>
 *{
 margin:0;
 padding:0;
 }
 
 .box{
 width:600px;
 height:400px;
 border:1px solid red;
 margin:100px auto;
 position:relative;
 }
 
 a{
 font-size:40px;
 position:absolute;
 text-decoration:none;
 top:-10px;
 }
 #prev{
 
 left:0;
 }
 #next{
 
 right:0;
 
 }
 #pos{
 margin-left:30px;
 }
 input{
 width:90px;
 height:40px;
 float:left;
 outline:none;
 border:0;
 }
 .box div{
 width:600px;
 height:400px;
 background:skyblue;
 text-align:center;
 line-height:300px;
 font-size:100px;
 font-weight:bold;
 text-shadow:5px 5px 5px #f90;
 display:none;
 }
 
 .box .show{
 display:block;
 }
 .box .active{
 width:88px;
 color:#fff;
 font-size:18px;
 font-weight:bold;
 background:#f90;
 }
 </style>
 <script>
 window.onload = function()
 {
 var oBox = document.getElementById('box');
 var oPrev = document.getElementById('prev');
 var oNext = document.getElementById('next');
 var aBtn = document.getElementsByTagName('input');
 var aDiv = oBox.getElementsByTagName('div');
 var oNow = 0;
 
 for (var i=0;i<aBtn.length;i++) {
 aBtn[i].dataIndex = i;
 
 aBtn[i].onclick = function(){
 
 oNow = this.dataIndex;
 
 for (var i=0;i<aBtn.length;i++) {
 aBtn[i].className = '';
 aDiv[i].className = '';
 }
 this.className = 'active';
 aDiv[this.dataIndex].className = 'show';
 }
 }
 
 oPrev.onclick = prev;
 oNext.onclick = next;
 
 //实现自动播放
 var timer = setInterval(next , 1000);
 
 oBox.onmouseover = function()
 {
 clearInterval(timer);
 }
 
 oBox.onmouseout = function()
 {
 timer = setInterval(next , 1000);
 }
 
 
 function prev()
 {
 oNow--;
 if (oNow < 0) {
 oNow = aBtn.length-1;
 }
 tab();
 }
 
 function next()
 {
 oNow++;
 if (oNow > aBtn.length-1) {
 oNow = 0;
 }
 
 tab();
 
 }
 
 function tab()
 {
 for (var i=0;i<aBtn.length;i++) {
 aBtn[i].className = '';
 aDiv[i].className = '';
 }
 aBtn[oNow].className = 'active';
 aDiv[oNow].className = 'show';
 }
 
 
 }
 </script>
 </head>
 
 <body>
 <div class="box" id="box">
 <a href="javascript:;" id="prev">☜</a>
 <a href="javascript:;" id="next">☞</a>
 <input type="button" name="" value="亚洲" class="active" id="pos"/>
 <input type="button" name="" value="欧洲" />
 <input type="button" name="" value="非洲" />
 <input type="button" name="" value="北美洲" />
 <input type="button" name="" value="南美洲" />
 <input type="button" name="" value="大洋洲" />
 <div class="show">亚洲</div>
 <div>欧洲</div>
 <div>非洲</div>
 <div>北美洲</div>
 <div>南美洲</div>
 <div>大洋洲</div>
 </div>
 </body>
</html>