路由配置：二级路由

{
path: '/login',
name: 'login',
component: login
},
{
path: '/',
name: 'layout',
component: layout,
children:[
{
path: '/',
name: 'home',
component: home
},
{
path: '/admin',
name: 'admin',
component: admin
},
{
path: '/user',
name: 'user',
// route level code-splitting
// this generates a separate chunk (about.[hash].js) for this route
// which is lazy-loaded when the route is visited.
component: user
},
]
},