The read-only href property of the CSSImportRule interface returns the URL specified by the @import at-rule.
The resolved URL will be the href attribute of the associated stylesheet.
A string.
The following stylesheet includes a single @import rule. Therefore the first item in the list of CSS rules will be a CSSImportRule. The href property returns the URL of the imported stylesheet.
@import "style.css" screen;const myRules = document.styleSheets[0].cssRules;
console.log(myRules[0].href); // 'style.css'