angular

Unknown element — component not declared (NG8001)

NG8001.*'([^']+)' is not a known element

Fixes

1.Import the module that exports the component into your feature module's imports array
2.If standalone component, add it to the `imports` array of the consuming component
3.Check the component's selector matches exactly what's in the template (including 'app-' prefix)

templatemodulesdeclarations

Related Errors

ExpressionChangedAfterItHasBeenCheckedError (NG0100)

NG0100.*Expression has changed after it was checked

•Move the value change to ngAfterViewInit with a ChangeDetectorRef.detectChanges() call
•Use setTimeout(() => { ... }) to defer the change to the next cycle

Circular dependency in DI (NG0200)

NG0200.*Circular dependency in DI detected

•Break the cycle by injecting one service lazily with `@Inject(forwardRef(() => ServiceName))`
•Extract shared logic into a third service that both services depend on

NullInjectorError — missing provider

NullInjectorError: No provider for (\w+)

•Add the service to the `providers` array of the module or component that needs it
•Use `@Injectable({ providedIn: 'root' })` on the service class for app-wide singleton