1 <!DOCTYPE html>
2 <html>
3 <head>
4 <meta charset="UTF-8">
5 <title></title>
6 <style type="text/css">
7 #box{
8 text-align: center;
9 }
10 #scrollImg{
11 margin-top: 200px;
12 width: 200px;
13 height: 200px;
14
15 }
16 </style>
17 </head>
18 <body>
19 <div id="box">
20 <img id="scrollImg" src="img/5.jpg" alt="加载失败" />
21 </div>
22 </body>
23 <script type="text/javascript">
24 // 获取到 img 标签
25 var picture = document.getElementById("scrollImg");
26 var count = 5;
27 setInterval(function(){
28 count++;
29 // 实现字符串的拼接
30 var imgName1 = count + ".jpg";
31 var imgName2 = "img/" + imgName1;
32 // 设置 img 标签的图片源
33 picture.src = imgName2;
34 // 方法1
35 // count = count % 3;
36 // 方法2
37 if(7 == count){
38 count = 4;
39 }
40 },3000);
41
42 </script>
43 </html>
原文：http://www.cnblogs.com/PowellZhao/p/5547127.html