The system property of the CSSCounterStyleRule interface gets and sets the value of the system descriptor. If the descriptor does not have a value set, this attribute returns an empty string.
A string.
The following example shows a @counter-style rule. In JavaScript, myRules[0] is this @counter-style rule, returning system gives us the value "fixed".
@counter-style box-corner {
system: fixed;
symbols: ◰ ◳ ◲ ◱;
suffix: ": ";
}let myRules = document.styleSheets[0].cssRules;
console.log(myRules[0].system); // "fixed"