element導航菜單控制當前菜單樣式

直接使用Element的導航菜單組件，參考官方文檔：http://element-cn.eleme.io/#/zh-CN/component/menu

問題1：設置當前的導航樣式，直接使用自帶屬性控制就能夠。

<el-menu :default-active="$route.path"
         :unique-opened="true"
         class="el-menu-demo"
         @select="handleSelect"
         background-color="rgba(0,0,0,0)"
         text-color="#fff"
         active-text-color="#ffd04b"
>
  <el-submenu index="1">
    <template slot="title">
      <!--<i class="el-icon-location"></i>-->
      <img src="/static/images/icon/ic1.png" alt="" class="ic-pic">
      <span>運營中心</span>
    </template>
    <el-menu-item-group>
      <el-submenu index="1-1">
        <template slot="title">
          <span>審覈中心</span>
        </template>
        <el-menu-item-group>
          <el-menu-item index="../index/auditHistory">
            技術員審覈
          </el-menu-item>
          <el-menu-item index="1-2">維保圓審覈</el-menu-item>
          <el-menu-item index="/index/propertyList">物業公司審覈</el-menu-item>
        </el-menu-item-group>
      </el-submenu>
      <el-menu-item index="/operation/businessList">業務列表</el-menu-item>
    </el-menu-item-group>
  </el-submenu>

  <el-submenu index="2">
    <template slot="title">
      <!--<i class="el-icon-location"></i>-->
      <img src="/static/images/icon/ic2.png" alt="" class="ic-pic">
      <span>電梯管理</span>
    </template>
    <el-menu-item-group>
      <el-menu-item index="/ElevatorManagement">
        統計看板
      </el-menu-item>
      <el-menu-item index="2-2">維保數據</el-menu-item>
      <el-menu-item index="">警報數據</el-menu-item>
      <el-menu-item index="/ElevatorManagement/ElevatorList">列表查看</el-menu-item>
    </el-menu-item-group>
  </el-submenu>
  <el-submenu index="8">
    <template slot="title">
      <!--<i class="el-icon-location"></i>-->
      <img src="/static/images/icon/ic1.png" alt="" class="ic-pic">
      <span>廣告管理</span>
    </template>
    <el-menu-item-group>
      <el-menu-item index="/advertisement/advertiserList">
        廣告列表
      </el-menu-item>
      <el-menu-item index="/advertisement/">廣告設置</el-menu-item>
    </el-menu-item-group>
  </el-submenu>
  <el-menu-item index="9">
    <img src="/static/images/icon/ic8.png" alt="" class="ic-pic">
    <span slot="title">大數據中心</span>
  </el-menu-item>
</el-menu>

@select="handleSelect"給菜單添加點擊事件
事件的定義：

handleSelect(key, keyPath) {　　//key是index屬性值，index能夠直接設置路徑。  this.$router.push({path:key})},這樣就完成了，點擊菜單跳轉後自動保存當前菜單的狀態。問題2：只保持一個菜單展開unique-opened 是否只保持一個子菜單的展開