web api instance property
Document: customElementRegistry property
The customElementRegistry read-only property of the Document interface returns the CustomElementRegistry object associated with this document, or null if one has not been set.
For documents associated with a Window (such as the main document of a page), this is the global CustomElementRegistry that is also accessible through the customElements property. Documents created programmatically (for example, via createHTMLDocument()) have a null custom element registry by default.
This property is also available on ShadowRoot objects via the same customElementRegistry property name.
Value
A CustomElementRegistry object, or null.
Examples
Accessing a document’s custom element registry
This example shows that the main document’s customElementRegistry is the same global registry available through customElements, while documents created programmatically via createHTMLDocument() have a null registry by default.
// The main document's registry is the global one:
console.log(document.customElementRegistry === window.customElements); // true (for Window-associated documents)
// Documents created programmatically have a null registry:
const newDoc = document.implementation.createHTMLDocument("New document");
console.log(newDoc.customElementRegistry); // null