案例：
代码：
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<style>
#wai{
margin: 50px auto;
border:1px solid;
width: 200px;
height: 300px;
background-color: aqua;
padding:10px;
text-align:center;
}
</style>
</head>
<body>
<div id="wai">
<p></p>
<img src="拼图效果/01.jpg" alt="1">
<button id="prev">上一张</button>
<button id="next">下一张</button>
</div>
<script>
var prev=document.getElementById("prev");
var next=document.getElementById("next");
var img=document.getElementsByTagName("img")[0];
var arr=["拼图效果/01.jpg","拼图效果/02.jpg","拼图效果/03.jpg","拼图效果/04.jpg","拼图效果/05.jpg","拼图效果/06.jpg"];
var index=0;
var p=document.getElementsByTagName("p")[0];
p.innerHTML="一共"+(arr.length-1)+"张，这是第"+(index+1)+"张"
prev.onclick=function(){
index--;
if(index<0){
index=arr.length-1;
}
img.src=arr[index];
p.innerHTML="一共"+(arr.length-1)+"张，这是第"+(index+1)+"张"
};
next.onclick=function(){
index++;
if(index>arr.length-1){
index=0;
}
img.src=arr[index];
p.innerHTML="一共"+(arr.length-1)+"张，这是第"+(index+1)+"张"
};
</script>
</body>
</html>