The CSSSupportsRule interface represents a single CSS @supports at-rule.
Inherits properties from its ancestors CSSConditionRule, CSSGroupingRule, and CSSRule.
Inherits methods from its ancestors CSSConditionRule, CSSGroupingRule, and CSSRule.
The CSS includes a CSS feature query using the @supports at-rule, containing one style rule. This will be the first CSSRule returned by document.styleSheets[0].cssRules. myRules[0] therefore returns a CSSSupportsRule object.
@supports (display: grid) {
body {
color: blue;
}
}let myRules = document.styleSheets[0].cssRules;
console.log(myRules[0]); // a CSSSupportsRule representing the feature query.