vue 设置 菜单Item 背景色

 <a-menu-item 
            @click = "selectItem" :class = 'child.id==selected? "selected":""'
            v-for="(child) in item.children" :key="child.id" >


 data () {
      return {
        spinning: false,
        selected:-1
        
      }


methods: {
      async onSelect (e) {
        this.$emit('select', { id: e.key })
      },
      selectItem(e){
        this.selected = e.key
      }


 .selected{
    background-color: aquamarine;
  }