父级：

<template>
  <div>
    <!-- <A @on-click="getFlag"></A>
    <B :flag="Flag"></B> -->
    <A></A>
    <B></B>
  </div>
</template>

<script setup lang="ts">
import { ref } from "vue";
import A from "./components/A.vue";
import B from "./components/B.vue";
// const Flag = ref(false);
// const getFlag = (params: boolean) => {
//   Flag.value = params;
// };
</script>
 

<style></style>

A组件：

<template>
  <div class="A">
    <button @click="emitB">派发一个事件</button>
  </div>
</template>

<script setup lang="ts">
// const emit = defineEmits(["on-click"]);
import  Bus  from  '../bus';

let flag = false;
const emitB = () => {
  flag = !flag;
  // emit("on-click", flag);
  Bus.emit('on-click',flag);
};


</script>

<style>
.A{
  width: 200px;
  height: 200px;
  color: #fff;
  background: blue;
}
</style>

B组件：

<template>
    <div class="B">
    <h1>B组件</h1>
    {{Flag}}
     </div>
</template>
  
<script setup lang='ts'>
import  Bus  from  "../Bus";
import  {ref} from  "vue";
let  Flag=ref(false);
Bus.on('on-click',(flag:boolean)=>{
  Flag.value=flag;
})
  // type  Props={
  //     flag:boolean
  // }
  // defineProps<Props>();

</script>
  
<style>
  .B{
    width:200px;
    height: 200px;
    color:#fff;
    background: red;
  }
</style>

Bus.ts:

type BusClass = {
    emit: (name:string) => void,
    on:(name:string,callback:Function)=>void
}

type Pramskey = string | number | symbol;

type List = {
    [key:Pramskey]:Array<Function> 
}

class Bus implements BusClass{
    list: List
    
    constructor() {
        this.list={}
    }
    emit(name: string,...args:Array<any>) {
        let evenentName:Array<Function> = this.list[name];
        evenentName.forEach(fn => {
            fn.apply(this,args)
        })
    
    }

    on(name:string,callback:Function) {
        let fn:Array<Function> = this.list[name] || [];
        fn.push(callback);
        this.list[name] = fn;
    }


}

export default new Bus();

效果图：