<el-menu :default-active="activeMenuPath" :collapse="isCollapse" :collapse-transition="false" :unique-opened="true" class="el-menu-vertical-demo" @select="handleMenuIndex" ></el-menu>
default-active 当前激活菜单的 index string
动态绑定activeMenuPath，通过@select进行路由跳转的同时保留当前高亮path