How to use global prompt box component in vue?

<template>
   <!-- 全局提示框 -->
   <p v-show="visible" class="dialog-tips dialog-center">
     <p>{{message}}</p>
   </p>
</template>
<script>
export default {
 data() {
  return {
   visible: false,
   message: ""
  };
 }
};
</script>
<style lang="scss">
.dialog-tips{
  position: fixed;
  z-index: 100;
  min-width: 220px;
  padding: 40px 22px;
  white-space: nowrap;
  background-color: #fff;
  box-shadow: 0px 8px 15px 0 rgba(0, 0, 0, 0.1);
  text-align: center;
  .dialog-tips-icon{
    width: 54px;
    height: 54px;
    @extend %bg-contain;
    display: inline-block;
    margin-bottom: 13px;
  }
}
.dialog-center {
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%)
}
</style>

import ToastComponent from './toast.vue'
const Toast = {};
// 注册Toast
Toast.install = function (Vue) {
  // 生成一个Vue的子类
  // 同时这个子类也就是组件
  const ToastConstructor = Vue.extend(ToastComponent)
  // 生成一个该子类的实例
  const instance = new ToastConstructor();
  // 将这个实例挂载在我创建的p上
  // 并将此p加入全局挂载点内部
  instance.$mount(document.createElement('p'))
  document.body.appendChild(instance.$el)
  // 通过Vue的原型注册一个方法
  // 让所有实例共享这个方法 
  Vue.prototype.$toast = (msg, duration = 1500) => {
    instance.message = msg;
    instance.visible = true;
    setTimeout(() => {
      instance.visible = false;
    }, duration);
  }
}
export default Toast

　import Vue from 'vue'
　　import Toast from './toast' 
　　Vue.use(Toast);

this.$toast("XXXXXXXXX");