<!DOCTYPE html>
<html>
<head>
<title>练习2</title>
<meta charset="UTF-8"/>
<script>
function myFunction(){
var num = Math.floor(Math.random()*3)+1; //可以通过修改随机数的值来修改随机图片数
document.getElementById("myImage").src = "../images/" + num + ".jpg";
}
</script>
</head>
<body>
<h2>点击按钮，切换图片</h2>
<img id="myImage" border="0" src="../images/1.jpg"><br>
<button onclick="myFunction()">切换</button>
</body>
</html>
效果
