Unexpected value 'undefined' declared by the module 'AppModule'

Question

What is wrong here? I'm trying to make it work but I get that error in the header. I have included the <router-outlet></router-outlet> in the app.component.html that is being templateUrl called by the app.component.ts, still no luck.

app.module.ts:

import { NgModule }             from '@angular/core'; import { BrowserModule }        from '@angular/platform-browser'; import { FormsModule }          from '@angular/forms'; import { RouterModule, Routes } from '@angular/router';   import { AppComponent }  from './app.component'; import { AppRoutingModule } from './app-routing.module'; import { TopnavComponent } from './components/navbars/topnav/topnav.component'; import { LeftnavComponent } from './components/navbars/leftnav/leftnav.component'; import { LeftnavsecondaryComponent } from './components/navbars/leftnav-secondary/leftnav-secondary.component'; import { WorldofwarcraftComponent } from './components/games/worldofwarcraft/worldofwarcraft.component';  @NgModule({     imports:    [ BrowserModule, FormsModule, AppRoutingModule ],     declarations:   [ AppComponent, TopnavComponent, LeftnavComponent, LeftnavsecondaryComponent, WorldofwarcraftComponent ],     bootstrap:  [ AppComponent ] })  export class AppModule { } 

app-routing.module.ts:

import { NgModule }              from '@angular/core'; import { RouterModule, Routes }  from '@angular/router';  import { WorldofwarcraftComponent } from './components/games/worldofwarcraft/worldofwarcraft.component';  const appRoutes: Routes = [   { path: 'worldofwacraft', component: WorldofwarcraftComponent } ];  @NgModule({   imports: [ RouterModule.forRoot(appRoutes) ],   exports: [ RouterModule ] })  export class AppRoutingModule {} 

Answer 1

I got the same error , sometimes this issue occur and you only need to re-run the server using ng serve or whatever CLI you use , as mentioned here