鼠标经过二级菜单的时候如果显示对应的三级菜单

<el-menu-item index="1" style="width: 68px" @mouseover.native="show=true" @mouseout.native="show=false" >产品

            <div v-show="show" class="menu_list" v-for="(item,index) in items">
              <li @mouseover='showList=true' @mouseout='showList=false' >{{item.a}}
                <div v-show="showList" class="menu_tree">
                  <el-col>
                    <span class="menu_sm">智能终端</span>
                    <span class="menu_sm">安全栅</span>
                    <span class="menu_sm">隔离器</span>
                    <span class="menu_sm">无纸记录仪</span>
                    <span class="menu_sm">浪涌保护器</span>
                    <span class="menu_sm">过程校验仪</span>
                  </el-col>
                </div>
              </li>
            </div>
          </el-menu-item>
          

<script>

export default {
  name: "header",
  data() {
    return{
      show: false,
      showList: false,
      items:[
        {
          'a':'现场仪表1',
          "children":[
            {
              'znzd':'智能终端',
              'znbsq':'智能变送器',
              'aql':'安全栅',
              'glq':'隔离器',
              'wzjly':'无纸记录仪',
              'lybhq':'浪涌保护器',
              'gcjyy':'过程校验仪',

            }
          ]
        },
        {
          'a':'控制阀2',
          "children":[
            {
              'znzd':'控制阀1',
            }
          ]
        },
        {
          'a':'辅助设备',
          "children":[
            {
              'znzd':'辅助设备1',
            }
          ]
        },
        {
          'a':'分析仪',
          "children":[
            {
              'znzd':'分析仪1',
            }
          ]
        }
      ]
    }
  },
  methods:{
    getIndex:function (index) {

    }
  }
}

</script>