VueJS - Vuefire - TypeError：document.onSnapshot 不是函数

如何解决VueJS - Vuefire - TypeError：document.onSnapshot 不是函数

我正在尝试在我的项目中实施 vuefire。我正在遵循 vuefire 网站上的指南，但仍然出现此错误。

db.js:

import firebase from 'firebase/app'
import 'firebase/firestore';
const firebaseConfig = {
apiKey: ....,authDomain: ....,projectId: ....,storageBucket: ...,messagingSenderId:....,appId: ..."
};
const app = firebase.initializeApp(firebaseConfig)
export const db = app.firestore()

main.js

    import Vue from 'vue';
import App from './App.vue';
import vuetify from './plugins/vuetify';
import { firestorePlugin } from 'vuefire'
import DatetimePicker from 'vuetify-datetime-picker';
Vue.use(firestorePlugin)
Vue.config.productionTip = false;
Vue.use(DatetimePicker)
new Vue({
vuetify,render: h => h(App)
}).$mount('#app');

App.vue

import { db } from "../db";
export default {
name: "App",data() {
return {
fireDB: [],},mounted() {

console.log(this.fireDB);
  },firestore: {
// fireDB: db.collection("something").doc('else').get().then((res) => {
//   console.log(res);
// }) - like this it gives me the error.

//fireDB: db.collection("something") - like this it returns an array with an object that is my database.
  },};

从控制台我看到调用 onSnapshot 的“文档”是一个承诺