files/en-us/web/api/elementinternals/ariaexpanded/index.md
{{APIRef("Web Components")}}
The ariaExpanded property of the {{domxref("ElementInternals")}} interface reflects the value of the aria-expanded attribute, which indicates whether a grouping element owned or controlled by this element is expanded or collapsed.
[!NOTE] Setting aria attributes on
ElementInternalsallows default semantics to be defined on a custom element. These may be overwritten by author-defined attributes, but ensure that default semantics are retained should the author delete those attributes, or fail to add them at all. For more information see the Accessibility Object Model explainer.
A string with one of the following values:
"true"
"false"
"undefined"
In this example the value of ariaExpanded is set to "true".
class CustomControl extends HTMLElement {
constructor() {
super();
this.internals_ = this.attachInternals();
this.internals_.ariaInvalid = "true";
}
// …
}
{{Specifications}}
{{Compat}}