$(selector).stop(true, false);
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
<style type="text/css">
* {
margin: 0;
padding: 0;
}
ul {
list-style: none;
}
.wrap {
width: 330px;
height: 30px;
margin: 100px auto 0;
padding-left: 10px;
background-color: pink;
}
.wrap li {
background-color: green;
}
.wrap > ul > li {
float: left;
margin-right: 10px;
position: relative;
}
.wrap a {
display: block;
height: 30px;
width: 100px;
text-decoration: none;
color: #000;
line-height: 30px;
text-align: center;
}
.wrap li ul {
position: absolute;
top: 30px;
display: none;
}
</style>
<script src="jquery-3.3.1.js"></script>
<script>
//入口函数
$(document).ready(function () {
//需求：鼠标放入一级li中，让他里面的ul显示。移开隐藏。
var jqli = $(".wrap>ul>li");
//绑定事件
jqli.mouseenter(function () {
$(this).children("ul").stop().slideDown(1000);
});
//绑定事件(移开隐藏)
jqli.mouseleave(function () {
$(this).children("ul").stop().slideUp(1000);
});
});
</script>
</head>
<body>
<div class="wrap">
<ul>
<li>
<a href="java script:void(0);">一级菜单1</a>
<ul>
<li><a href="java script:void(0);">二级菜单2</a></li>
<li><a href="java script:void(0);">二级菜单3</a></li>
<li><a href="java script:void(0);">二级菜单4</a></li>
</ul>
</li>
<li>
<a href="java script:void(0);">二级菜单1</a>
<ul>
<li><a href="java script:void(0);">二级菜单2</a></li>
<li><a href="java script:void(0);">二级菜单3</a></li>
<li><a href="java script:void(0);">二级菜单4</a></li>
</ul>
</li>
<li>
<a href="java script:void(0);">三级菜单1</a>
<ul>
<li><a href="java script:void(0);">三级菜单2</a></li>
<li><a href="java script:void(0);"