Error in Using custom elements page sample code

[crysaro]

MDN URL

https://developer.mozilla.org/en-US/docs/Web/API/Web_components/Using_custom_elements#customized_built-in_elements

What specific section or headline is this issue about?

Customized built-in elements

What information was incorrect, unhelpful, or incomplete?

The demo on

https://developer.mozilla.org/en-US/docs/Web/API/Web_components/Using_custom_elements#customized_built-in_elements

throws the following error;

Uncaught TypeError: Illegal constructor.

What did you expect to see?

It should not throw an error

Do you have any supporting links, references, or citations?

No response

Do you have anything more you want to share?

the link to github in the docs show different code https://github.com/mdn/web-components-examples/blob/main/expanding-list-web-component/main.js

When I replace:

super(); wiith

self = super();

I get Uncaught ReferenceError: must call super constructor before using 'this' in derived class constructor

Tested in Chrome and FF in mac

[crysaro]

sorry about this

I missed the , { extends: "ul" } in the customElements.define