vueRouter.beforeEach((to, from, next) => {
  //store的getters中定义获取用户信息的函数 getUser
  //userId为空说明用户未登录
  let isLogin = store.getters.getUser.userId;
  if (!isLogin) {//未登录
    if (to.path !== '/login') {//跳转到登录页
      return next({path: '/login'});
    }else {
      next();
    }
  }else {//已登录
    if (to.path === '/login') {//跳转到首页
      return next({path: '/index'});
    }
    next();
  }
});