How to initialize the Vue app depending on back-end response first?

Question

I want some code to be ran before anything else in the app, that code will send a request to the Back-end and then update the store. I need that part to be executed first because route guards depend on it, how to achieve that?

Code Example

Fetching user information & settings

async init() {
    await AuthService.initCSRF();
    await AuthService.getUser().then((res) => {
      if (res.data && res.data.user) {
        this.loginLocally(res.data.user);
      } else {
        this.logoutLocally();
      }
    });
}

Auth guard

export function isLoggedIn(to, from, next) {
  console.log('Checked', store.state.auth.isLoggedIn);
  if (store.state.auth.isLoggedIn) {
    next();
    return;
  }

  next({ name: 'login' })
}

Answer 1

in my old project, I did something like this. hope you get some idea.

app.js

import App from './components/App.vue'
store.dispatch('auth/attempt', sessionStorage.getItem('token')).then(() =>{
new Vue({
    el: '#app',
    router,
    store,
    render: h => h(App),
 });
});

here I'm validating the token saved in local storage before rendering the app.

my Vuex actions something like this

async signIn({dispatch}, credentials) {
  let response = await axios.post("auth/signin", credentials);
  await dispatch('attempt', response.data.token)
},


async attempt({commit, state}, token) {
  if (token) {
    await commit('SET_TOKEN', token);

  }
  if (!state.token) {
    return;
  }

  try {
    let response = await axios.get('auth/me');
    commit('SET_USER', response.data)
  } catch (e) {
    commit('SET_TOKEN', null);
    commit('SET_USER', null);
  }
},
async signOut({commit}) {
  axios.post('auth/signout').then(() => {
    commit('SET_TOKEN', null);
    commit('SET_USER', null);
  });
}

I'm using a subscriber to listen to mutations and add or remove token in request headers

import store from '../store'

store.subscribe((mutation) => {

 if (mutation.type === 'auth/SET_TOKEN') {
  if (mutation.payload) {
   axios.defaults.headers.common['Authorization'] = `Bearer ${mutation.payload}`;
  sessionStorage.setItem('token', mutation.payload);
} else {
  axios.defaults.headers.common['Authorization'] = null;
  sessionStorage.removeItem('token');
  }
 }
});

Finally an axios interceptor for handle token expiration.

import router from '../plugins/router'
import store from '../store'
import axios from "axios";

axios.interceptors.response.use((response) => {

  return response;
}, (error) => {
if (error.response.status) {
  if (error.response.status === 401) {

  if (router.currentRoute.name !== 'landing') {
    store.dispatch('auth/clearToken').then(() => {
      router.replace({
        name: 'landing'
      });

    }).finally(() => {
      swal.fire(
        'Your Session is Expired',
        'Please sign in again!',
        'error'
      )
    });
    }
  }
}

return Promise.reject(error);
});