StyleSheet: parentStyleSheet property

Baseline Widely available

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

The parentStyleSheet property of the StyleSheet interface returns the style sheet, if any, that is including the given style sheet.

// Find the top level stylesheet
const sheet = stylesheet.parentStyleSheet ?? stylesheet;

This property returns null if the current stylesheet is a top-level stylesheet or if stylesheet inclusion is not supported.

Specification
CSS Object Model (CSSOM) # dom-stylesheet-parentstylesheet

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