在没出父div的情况下，对着子div十进十出，打印结果如下
mouseover：
- div1，
- div2、div1，
- div1，
- div2、div1
子div先触发，冒泡的意思吧
mouseenter：
- div2
- div2
- div2
div1不会触发
测试代码
<!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>Document</title>
<style>
.div1 {
width: 200px;
height: 200px;
background-color: aqua;
position: relative;
left: 0;
}
.div2 {
width: 100px;
height: 100px;
background-color: red;
position: absolute;
left: 200px;
}
</style>
</head>
<body>
<div class="div1">
<div class="div2"></div>
</div>
<script>
const div1 = document.getElementsByClassName("div1")[0]
const div2 = document.getElementsByClassName("div2")[0]
div1.addEventListener("mouseenter", function () {
console.log("div1")
})
div2.addEventListener("mouseenter", function () {
console.log("div2")
})
</script>
</body>
</html>
