vue-router2.0 怎么设置404页面 ？

Question

如题

routes: [
    { name: 'a', path: '/', component: a },
    { name: 'b', path: '/b/', component: b }
  ]

Answer 1

const router = new VueRouter({
    mode: 'history',
    routes: [
        { path: '*', component: NotFoundComponent }
    ]
})

Answer 2

当路由存在但是出错的时候呢？