CSSNamespaceRule

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

The CSSNamespaceRule interface describes an object representing a single CSS @namespace at-rule.

Inherits properties from its ancestor CSSRule.

CSSNamespaceRule.namespaceURI: Returns a string containing the text of the URI of the given namespace.
CSSNamespaceRule.prefix: Returns a string with the name of the prefix associated to this namespace. If there is no such prefix, returns an empty string.

Inherits methods from its ancestor CSSRule.

The stylesheet includes a namespace as the only rule. Therefore the first CSSRule returned will be a CSSNamespaceRule.

css

@namespace url(http://www.w3.org/1999/xhtml);

let myRules = document.styleSheets[0].cssRules;
console.log(myRules[0]); //a CSSNamespaceRule

Specification
CSS Object Model (CSSOM) # the-cssnamespacerule-interface

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