207、vue-router嵌套命名视图

/settings/emails//此后如有路径，则继续匹配
/settings/profile
以下是UserSettings.vue的定义
<div>
  <h1>UserSettings.vue</h1>
  <NavBar/>
  <router-view/>
  <router-view name="helper"/>
</div>
{
  path: ‘/settings‘,
  component: UserSettings,
  children: [{
    path: ‘emails‘,
    component: UserEmailsSubscriptions//正常匹配到<router-view/>
  }, {
    path: ‘profile‘,
    components: {
      default: UserProfile,//默认匹配到<router-view/>
      helper: UserProfilePreview
    }
  }]
}