How to load child route by default in angular 2

Add empty path routes as redirect automatically

const appRoutes: Routes = [
    {
        path:'',
        redirectTo: 'a',
        pathMatch: 'full' 
    },
    {
        path: 'a',
        component: AComponent,
        children:[
            {
                path:'',
                redirectTo: 'x',
                pathMatch: 'full' 
            },
            {
                path:'x',
                component: AXcomponent 
            }
        ]
    },
    { 
        path: 'b',
        component: bComponent
    }
];