html
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>学习Js</title>
<script src="js/index.js" type="text/javascript" charset="utf-8"></script>
</head>
<body>
<div id="picwrap">
<img src="img/jg1.jpg" id="mypic"/>
</div>
<div id="butwrap">
<button id="prebutton">上一张</button>
<button id="nextbutton">下一张</button>
</div>
</body>
</html>
js
curr = 1; //初始为1
function changepic(){
var pic = document.getElementById("mypic");
pic.src = 'img/jg' + curr + '.jpg';
}
window.onload = function (){
document.getElementById("prebutton").addEventListener('click',function(){
if(curr>1){
curr --;
changepic()
}
},false);
document.getElementById("nextbutton").addEventListener('click',function(){
if(curr<4){
curr ++;
changepic()
}
},false);
}
