新人练手，利用html引入element导航菜单，运行后无法正常显示菜单（显示结果如下图），使用的CDN引入element组件，代码如下：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title></title>
<link rel="stylesheet" href="https://unpkg.com/element-ui/lib/theme-chalk/index.css">
<script src="https://lib.baomitu.com/vue/2.6.14/vue.min.js"></script>
<script src="https://unpkg.com/element-ui/lib/index.js"></script>
</head>
<body>
<div id="app">
<el-button type="success">成功按钮</el-button>
<el-button @click="visible = true">Button</el-button> </div>
<div id="a">
<div class="line"></div>
<el-menu
:default-active="activeIndex2"
class="el-menu-demo"
mode="horizontal"
@select="handleSelect"
background-color="#545c64"
text-color="#fff"
active-text-color="#ffd04b">
<el-menu-item index="1">处理中心</el-menu-item>
<el-submenu index="2">
<template slot="title">我的工作台</template>
<el-menu-item index="2-1">选项1</el-menu-item>
<el-menu-item index="2-2">选项2</el-menu-item>
<el-menu-item index="2-3">选项3</el-menu-item>
<el-submenu index="2-4">
<template slot="title">选项4</template>
<el-menu-item index="2-4-1">选项1</el-menu-item>
<el-menu-item index="2-4-2">选项2</el-menu-item>
<el-menu-item index="2-4-3">选项3</el-menu-item>
</el-submenu>
</el-submenu>
<el-menu-item index="3" disabled>消息中心</el-menu-item>
<el-menu-item index="4"><a href="https://www.ele.me" target="_blank">订单管理</a></el-menu-item>
</el-menu>
</div>
</body>
<script type="text/javascript" >
const vm = new Vue({
el: '#app',
data(){
}
})
</script>
<script type="text/javascript" >
const vm = new Vue({
el: '#a',
data(){
}
})
</script>
</html>
困惑了好几天，不知原因在哪，请各位技术大佬帮忙指出原因，非常感谢！！！
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title></title>
<link rel="stylesheet" href="https://unpkg.com/element-ui/lib/theme-chalk/index.css">
<script src="https://lib.baomitu.com/vue/2.6.14/vue.min.js"></script>
<script src="https://unpkg.com/element-ui/lib/index.js"></script>
</head>
<body>
<div id="app">
<el-button type="success">成功按钮</el-button>
<el-button @click="visible = true">Button</el-button> </div>
<div id="a">
<div class="line"></div>
<el-menu
:default-active="activeIndex2"
class="el-menu-demo"
mode="horizontal"
@select="handleSelect"
background-color="#545c64"
text-color="#fff"
active-text-color="#ffd04b">
<el-menu-item index="1">处理中心</el-menu-item>
<el-submenu index="2">
<template slot="title">我的工作台</template>
<el-menu-item index="2-1">选项1</el-menu-item>
<el-menu-item index="2-2">选项2</el-menu-item>
<el-menu-item index="2-3">选项3</el-menu-item>
<el-submenu index="2-4">
<template slot="title">选项4</template>
<el-menu-item index="2-4-1">选项1</el-menu-item>
<el-menu-item index="2-4-2">选项2</el-menu-item>
<el-menu-item index="2-4-3">选项3</el-menu-item>
</el-submenu>
</el-submenu>
<el-menu-item index="3" disabled>消息中心</el-menu-item>
<el-menu-item index="4"><a href="https://www.ele.me" target="_blank">订单管理</a></el-menu-item>
</el-menu>
</div>
</body>
<script type="text/javascript" >
const vm = new Vue({
el: '#app',
data(){
}
})
</script>
<script type="text/javascript" >
const vm = new Vue({
el: '#a',
data(){
}
})
</script>
</html>
困惑了好几天，不知原因在哪，请各位技术大佬帮忙指出原因，非常感谢！！！
