Checking if app-custom exits in Angular html template

Question

I think I have a knot in my brain, it can't be that difficult.

I have an Angular component and it is called in my app.html <app-custom></app-custom> and if app-custom does not exist, a default component should be called instead <app-default></app-default>

I don't know how to check if the app-custom component exits or not.

you'd probably get an exception at build-time. You should probably move that logic into the component itself. What's the use-case? — browsermator
– browsermator, Commented Jul 9 at 16:42
what does the piece "if app-custom does not exist" mean? Is that not a component in your application code? I think if you expand this one the community could help you — Andrei
– Andrei, Commented Jul 9 at 17:48
Its a standard for many projects and in some this component exists, in other not. So i want to test if it exists and than call it other wise call an always existing default component. So we not always have to change it — pepenipf
– pepenipf, Commented Jul 10 at 3:40
@browsermator no if it not exists and i call it i don't get an error, i get a blank page — pepenipf
– pepenipf, Commented Jul 10 at 3:41

Naren Murali · Accepted Answer · 2025-07-10 07:07:18Z

1

Option 1:

We can add the default component inside the custom component, the default will be displayed, if the custom component does not exist. But you need to ensure there is no ng-content inside the custom component, else the default component will render inside the custom component.

index.html

<app-custom>
  <app-default></app-default>
</app-custom>

Option 2:

Create a root component app-root which always exists.

Then use @defer and @error to create the fallback, we need to add this to the app-root component.

@defer {
  <app-custom></app-custom>
} @error {
  <app-default></app-default>
}

answered Jul 10 at 7:07

Naren Murali

66.3k6 gold badges51 silver badges97 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

pepenipf Jul 10 at 11:04

ah, I knew it had to be really easy, but sometimes you just make stupid mistakes. Thank you! Option 2 doesn't work for me somehow, but option 1 works perfectly

Collectives™ on Stack Overflow

Checking if app-custom exits in Angular html template

1 Answer 1

Option 1:

index.html

Option 2:

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Option 1:

index.html

Option 2:

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related