javascript - 如何在 .addEventListener 中访问 Vue.prototype？

Question

我正在尝试访问 Vue.prototype.$firebase 的全局对象在 main.js 中声明

import Vue from "vue";
import App from "./App.vue";
import router from "./router";
import VueTailwind from "vue-tailwind";
import { FirebaseApp } from "@/firebase/firebase";
//Style
import "@/assets/styles/app.css";
import settings from "@/assets/styles/Tailwind.js";

FirebaseApp.auth().onAuthStateChanged((user)=>{
  Vue.prototype.$user = user;
})

//Vue
Vue.config.productionTip = false;
Vue.use(VueTailwind, settings);
Vue.prototype.$firebase = FirebaseApp;

new Vue({
  router,
  render: h => h(App)
}).$mount("#app");

内部 Login成分

<script>
export default {
  name: "Login",
  mounted: function () {
    this.submit();
  },
  methods: {
    submit() {
      let login = document.getElementById("login");     
      login.addEventListener(
        "submit",
        function (event) {
          event.preventDefault();
          const email = login.email.value;
          const password = login.password.value;
          this.$firebase
            .auth()
            .signInWithEmailAndPassword(email, password)
            .then((user) => {
              console.log(user)
              this.$router.replace('/')
            })
            .catch((error) => {
              console.log(error);
            });
        },
        true
      );
    },
  },
};
</script>

但我得到 TypeError: Cannot read property 'auth' of undefined ，同 this.$router .
但是在 .addEvenListener之外实例化对象打印效果很好，让我可以通过 let signIn 访问，但这不是我想要的行为，相反，我想在 login 之间“自动”路由和一个 dashboard在 onAuthStateChange通过使用 Vue.prototype.$firebase 而不是本地实例化进行登录:

<script>
export default {
  name: "Login",
  mounted: function () {
    this.submit();
  },
  methods: {
    submit() {
      let login = document.getElementById("login");
      let signIn = this.$FirebaseApp;
      let onLogin = this.$router;
      login.addEventListener(
        "submit",
        function (event) {
          event.preventDefault();
          const email = login.email.value;
          const password = login.password.value;
          signIn
            .auth()
            .signInWithEmailAndPassword(email, password)
            .then((user) => {
              console.log(user)
              onLogin.replace('/')
            })
            .catch((error) => {
              console.log(error);
            });
        },
        true
      );
    },
  },
};
</script>

访问 Vue.prototype.$firebase的正确方法是什么？为什么它有这样的范围限制？

Answer 1

避免使用 function()内部组件回调并使用 arrow functions反而。function创建自己的 this上下文，以便 this将不再引用组件，但箭头函数使用周围的 this语境:

login.addEventListener(
  "submit",
  (event) => {   // Changed to arrow function
  ...            // Now you can access `this.$firebase`
  },
  true
);