<html>
<head>
<meta charset="utf-8" />
<title></title>
<script type="text/javascript">
window.onload=function(){
var img=document.getElementById('img');
var num=0;
var a=['img/16.jpg','img/2.jpg','img/2 (12).jpg','img/2(13).jpg'];
var btn1=document.getElementById('btn1');
var btn2=document.getElementById('btn2');
btn1.onclick=function(){
num++;
if(num==4){
num=0;
}
img.src=a[num];
}
btn2.onclick=function(){
if(num==0){
num=4;
}
num--;
img.src=a[num];
}
}
</script>
</head>
<body>
<img src="img/16.jpg" height="400px" width="400px" id="img" />
<input type="button" value="+" id="btn1" />
<input type="button" value="-" id="btn2" />
</body>
</html>