CSSImportRule.href

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 USVString.

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 url("style.css") screen;

let myRules = document.styleSheets[0].cssRules;
console.log(myRules[0].href); //returns style.css