监听子组件值的变化

父传子prop
子传父emit

父监听子，可以用到hook，监听子组件数据的变化,也可以用vuex
也可以用emit方法此处
父组件

<el-tab-pane name="fourth">
            <span slot="label">样车申请单<el-badge :value="VehicleApplyTodoNum" class="item" /></span>
            <VehicleApplyTodo ref="VehicleApplyTodo" @hook:updated="getVehicleApplyTodoNum" />
          </el-tab-pane>

import VehicleApplyTodo from './component/vehiclemng/TodoEvent'
export default {
  name: 'Dashboard',
  components: {
    VehicleApplyTodo
  },
  data() {
    return {
      VehicleApplyTodoNum: null
    }
  },
method:{
getVehicleApplyTodoNum() {
      this.VehicleApplyTodoNum = this.$refs.VehicleApplyTodo.vsapplytotal
    }
}

子组件

data(){
vsapplytotal:0
}
created() {
    this.getApplys()
  },
  methods: {
    async getApplys() {
      const res = await getVSAEvent(this.tbapplylistQuery)
      this.vsapplytotal = res.result.total
    }