The cssRules property of the CSSGroupingRule interface returns a CSSRuleList containing a collection of CSSRule objects. 
 The cssRules property of the CSSGroupingRule interface returns a CSSRuleList containing a collection of CSSRule objects. 
a CSSRuleList.
js
let myRules = document.styleSheets[0].cssRules; console.log(myRules);
| Specification | 
|---|
| CSS Object Model (CSSOM)  # dom-cssgroupingrule-cssrules  | 
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | |
cssRules | 
45 | 12 | 20 | No | 32 | 3 | 45 | 45 | 20 | 32 | 2 | 5.0 | 
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    https://developer.mozilla.org/en-US/docs/Web/API/CSSGroupingRule/cssRules