The ownerNode property of the StyleSheet interface returns the node that associates this style sheet with the document.
This is usually an HTML <link> or <style> element, but can also return a processing instruction node in the case of <?xml-stylesheet ?>.
<html lang="en">
<head>
<link rel="stylesheet" href="example.css" />
</head>
<body>
<button onclick="alert(document.styleSheets[0].ownerNode)">
Show example.css's ownerNode
</button>
</body>
</html>
// Displays "object HTMLLinkElement"
For style sheets that are included by other style sheets, such as with @import, the value of this property is null.