VUE 结合 router 实现全局拦截，验证用户是否登录，没有登录的话，跳到登录界面

router.beforeEach((to,from,next)=>{
  if(to.path ==='/login'){
    next();
  }else {
    let token = localStorage.getItem('userInfo');
    if(token === null || token === ''){
      next('/login');
    }else {
      next();
    }
  }
});