路由中间件，导航之前验证auth

1. 需求：每次用户刷新页面时，会需要做token校验，但不刷新页面就不会进行请求发送

2. 说明：前后端分离开发，使用redis做用户信息缓存。token为用户校验的负载，考虑如果用户不刷新页面，会出现什么，因为localStorage不会过期，考虑Cookie的关联。

3. 代码：

import router from './router'
import store from './store'
import {Message} from 'element-ui'
import NProgress from 'nprogress' // progress bar
import 'nprogress/nprogress.css' // progress bar style
import {getToken} from '@/utils/auth' // get token from localStorage
import getPageTitle from '@/utils/get-page-title'

NProgress.configure({showSpinner: false}) // NProgress Configuration

const whiteList = ['/login'] // 白名单

router.beforeEach(async (to, from, next) => {
  // start progress bar
  NProgress.start()
  // set page title
  document.title = getPageTitle(to.meta.title)
  // determine whether the user has logged in
  const hasToken = getToken();
  if (hasToken) {
    if (to.path === '/login') {
      // if is logged in, redirect to the home page,如果已经登陆，还要访问登陆页面，则重定向到首页
      next({path: '/'});
      NProgress.done()
    } else {
      // 在vuex中保存有用户信息的，直接通过
      const hasGetUserInfo = store.getters.name;
      if (hasGetUserInfo) {
        next()
      } else {
        try {
          // 首次保存用户信息
          await store.dispatch('user/getInfo')
          next()
        } catch (error) {
          // remove token and go to login page to re-login
          await store.dispatch('user/resetToken')
          Message.error(error || 'Has Error')
          next(`/login?redirect=${to.path}`)
          NProgress.done()
        }
      }
    }
  } else {
    /* has no token*/

    if (whiteList.indexOf(to.path) !== -1) {
      // in the free login whitelist, go directly
      next()
    } else {
      // other pages that do not have permission to access are redirected to the login page.
      next(`/login?redirect=${to.path}`)
      NProgress.done()
    }
  }
});

router.afterEach(() => {
  // finish progress bar
  NProgress.done()
});