element-plus默认菜单打开步骤

<template>
  <el-menu :default-active="activeIndex" class="el-menu-vertical-demo">
    <el-sub-menu index="1">
      <template #title>
        <el-icon><location /></el-icon>
        <span>导航一</span>
      </template>
      <el-menu-item index="1-1">选项1</el-menu-item>
      <el-menu-item index="1-2">选项2</el-menu-item>
      <el-menu-item index="1-3">选项3</el-menu-item>
    </el-sub-menu>
    <el-menu-item index="2">
      <el-icon><document /></el-icon>
      <template #title>导航二</template>
    </el-menu-item>
    <el-menu-item index="3" disabled>
      <el-icon><setting /></el-icon>
      <template #title>导航三</template>
    </el-menu-item>
  </el-menu>
</template>
<script setup>
import { ref } from 'vue';
import { Location, Document, Setting } from '@element-plus/icons-vue';
const activeIndex = ref('1-1');  // 默认激活 "1-1" 菜单项
</script>

<template>
  <el-menu :default-active="['1-1', '2']" class="el-menu-vertical-demo">
    <el-sub-menu index="1">
      <template #title>
        <el-icon><location /></el-icon>
        <span>导航一</span>
      </template>
      <el-menu-item index="1-1">选项1</el-menu-item>
      <el-menu-item index="1-2">选项2</el-menu-item>
      <el-menu-item index="1-3">选项3</el-menu-item>
    </el-sub-menu>
    <el-menu-item index="2">
      <el-icon><document /></el-icon>
      <template #title>导航二</template>
    </el-menu-item>
    <el-menu-item index="3" disabled>
      <el-icon><setting /></el-icon>
      <template #title>导航三</template>
    </el-menu-item>
  </el-menu>
</template>
<script setup>
import { ref } from 'vue';
import { Location, Document, Setting } from '@element-plus/icons-vue';
const activeIndex = ref(['1-1', '2']);  // 默认激活 "1-1" 和 "2" 菜单项
</script>

<template>
    <template v-for="(item, index) in menuList" :key="index">
        <!-- 没有子路由 -->
        <template v-if="!item.children">
            <el-menu-item v-if="!item.meta.hidden" :index="item.path" @click="goRoute">
                <el-icon>
                    <component :is="item.meta.icon"></component>
                </el-icon>
                <template #title>
                    <span>{{ item.meta.title }}</span>
                </template>
            </el-menu-item>
        </template>
        <!-- 只有一个子路由 -->
        <template v-if="item.children && item.children.length == 1">
            <el-menu-item v-if="!item.children[0].meta.hidden" :index="item.children[0].path" @click="goRoute">
                <el-icon>
                    <component :is="item.children[0].meta.icon"></component>
                </el-icon>
                <template #title>
                    <span>{{ item.children[0].meta.title }}</span>
                </template>
            </el-menu-item>
        </template>
        <!-- 有多个子路由 -->
        <el-sub-menu v-if="item.children && item.children.length > 1" :index="item.path">
            <template #title>
                <el-icon>
                    <component :is="item.meta.icon"></component>
                </el-icon>
                <span>{{ item.meta.title }}</span>
            </template>
            <Menu :menuList="item.children"></Menu>
        </el-sub-menu>
    </template>
</template>
<script setup lang="ts">
import { useRouter } from 'vue-router'
// 引入路由器
const $router = useRouter()
// 获取父组件传递的数据
defineProps(['menuList'])
// 点击菜单的回调
const goRoute = (vc: any) => {
    // 路由跳转
    $router.push(vc.index)
}
</script>
<script lang="ts">
export default {
    name: 'Menu'
}
</script>
<style scoped></style>

<template>
    <div class="layout_container">
        <!-- 左侧菜单 -->
        <div class="layout_slider">
            <Logo></Logo>
            <!-- 展示菜单 -->
            <!-- 滚动组件 -->
            <el-scrollbar class="scrollbar">
                <!-- 菜单组件 -->
                <el-menu background-color="#2e2e2e" text-color="white" active-text-color="yellowgreen" :default-active="$route.path">
                    <Menu :menuList="userStore.menuRoutes"></Menu>
                </el-menu>
            </el-scrollbar>
        </div>
        <!-- 顶部导航 -->
        <div class="layout_tabbar">456</div>
        <!-- 内容展示区域 -->
        <div class="layout_main">
            <Main></Main>
        </div>
    </div>
</template>
<script setup lang="ts">
// 引入左侧菜单logo子组件
import Logo from './logo/index.vue'
// 引入菜单组件
import Menu from './menu/index.vue'
// 右侧内容的展示区
import Main from './main/index.vue'
// 获取路由对象
import { useRoute } from 'vue-router';
// 获取用户相关的小仓库
import useUserStore from '@/store/modules/user';
let userStore = useUserStore();
// 获取路由对象
let $route = useRoute();
</script>
<style scoped lang="scss">
.layout_container {
    width: 100%;
    height: 100vh;
    background-color: red;
    .layout_slider {
        width: $base-menu-width;
        height: 100vh;
        background-color: $base-menu-bg;
        .scrollbar {
            width: $base-menu-width;
            height: calc(100vh - $base-menu-logo-height);
            .el-menu {
                border-right: none;
            }
        }
    }
    .layout_tabbar {
        position: fixed;
        width: calc(100% - $base-menu-width);
        height: $base-tabbar-height;
        background-color: cyan;
        top: 0px;
        left: $base-menu-width;
    }
    .layout_main {
        position: fixed;
        width: calc(100% - $base-menu-width);
        height: calc(100% - $base-tabbar-height);
        background-color: yellow;
        top: $base-tabbar-height;
        left: $base-menu-width;
        padding: 20px;
        overflow: auto;
    }
}
</style>