Angular `<router-outlet>` displays template twice

Question

I'm using angular4 and trying to create a router link. The router link works but displays the template twice.

Below is my code in the component:

import { Component } from '@angular/core';
import { Router, ActivatedRoute } from '@angular/router';

@Component({
  selector: 'app-root',
  template: `
  <h1>Contacts App</h1>
    <ul>
      <li><a [routerLink]="['/facebook/top']">Contact List</a></li>
    </ul>
    <router-outlet></router-outlet>
    `
})
export class AppComponent {
    constructor(
        private route: ActivatedRoute,
        private router: Router,
    ){ }

    gotoDetail(): void {
        this.router.navigate(['facebook/top']);
    }
}

my routes:

const routes: Routes = [
  { path: '', component: AppComponent },
  { path: 'facebook/top',  component: CommentComponent },
];

@NgModule({
  imports: [ RouterModule.forRoot(routes) ],
  exports: [ RouterModule ]
})
export class AppRoutingModule {}

Answer 1

Your default route points to AppComponent, so your route is rendering the AppComponent inside the AppComponent.

Create a DashboardComponent or HomeComponent for this. And then do:

{ path: '', component: DashboardComponent }

Update 1:

As @GünterZöchbauer mentioned, we should add pathMatch: 'full' for "an empty path route with no children".

So we can go with the AppComponent approach (check Günter's answer):

{ path: '', component: AppComponent, pathMatch: 'full' }

Or, the DashboardComponent approach as I stated above in my answer.

Answer 2

Why is this happening?

1) In your application entry point, most likely main.ts, one can read this line:

platformBrowserDynamic().bootstrapModule(AppModule);

This tells angular to bootstrap the module AppModule

2) In AppModule, one can find this line:

bootstrap: [ AppComponent ]

This tells angular to bootstrap the component AppComponent. This is why you see the first Contacts App part, because the html template of the AppComponent is:

<h1>Contacts App</h1>
<ul>
    <li><a [routerLink]="['/facebook/top']">Contact List</a></li>
</ul>
<router-outlet></router-outlet>

3) However, the template of your AppComponent also contains <router-outlet>. The router reads the routes configuration, accordingly creates a new instance of AppComponent and inject it right after the element <router-outlet>. This is why you see the second Contacts App part.

Answer 3

If you have an empty path route with no children, use pathMatch: 'full'

instead of

{ path: '', component: AppComponent },

use

{ path: '', component: AppComponent, pathMatch: 'full' },

and what @SrAxi said.

Answer 4

In your app-routing.module.ts file try to use:

{path: '' , redirectTo: 'AppComponent', pathMatch: 'full'}

instead of:

{ path: '', component: AppComponent, pathMatch: 'full' }