<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>onmouseover+get/setAttribute</title>
<style>
*{
margin: 0;
padding: 0;
}
ul{
list-style: none;
}
ul li{
width: 50px;
height: 50px;
margin-top: 10;
margin-left: 10px;
float: left;
text-align: center;
line-height: 50px;
overflow: hidden;
}
ul li.active{
border: 1px solid red;
}
</style>
</head>
<body>
<img src="../images/img01.jpg" id="imgBig" width="300" height="300" >
<ul>
<li class="active"><a href=""><img src="../images/img01.jpg" width="45" height="45" class="imgSmall"></a></li>
<li><a href=""><img src="../images/img02.jpg" width="45" height="45" class="imgSmall"></a></li>
<li><a href=""><img src="../images/img03.jpg" width="45" height="45" class="imgSmall"></a></li>
<li><a href=""><img src="../images/img04.jpg" width="45" height="45" class="imgSmall"></a></li>
<li><a href=""><img src="../images/img05.jpg" width="45" height="45" class="imgSmall"></a></li>
</ul>
<script>
//1. 准备事件源
let imgBig=document.getElementById("imgBig");
let imgSmalls=document.getElementsByClassName("imgSmall");
//2. 遍历集合，
for (let i = 0; i < imgSmalls.length; i++) {
//2.1 为小图片注册鼠标悬停事件
imgSmalls[i].onmouseover=function(){
//2.2 内部遍历 清空class 属性
for (let j = 0; j < imgSmalls.length; j++) {
imgSmalls[j].parentNode.parentNode.setAttribute("class","");
}
// 遍历获取每一个小图的src 赋值给大图的src 效果呈现:大图随着小图改变
let imgSrc=this.getAttribute("src");
console.log(imgSrc);
imgBig.setAttribute("src",imgSrc);
// 2.3 为每个li设置class="active" 鼠标悬停 边框变红
this.parentNode.parentNode.setAttribute("class","active");
}
}
</script>
</body>
</html>
javascript-demo01-onmouseover-鼠标悬停事件
原文：https://www.cnblogs.com/ABC-wangyuhan/p/14541451.html