10 router

https://router.vuejs.org/zh/guide/advanced/navigation-guards.html

1.路由守卫beforeEach

router.beforeEach((to, from, next) => {
  let username = localStorage.getItem('username')
  if (to.name === 'login' || to.name === 'register') next()
  else if (!username) next({ name: 'login' })
  else next()
})