The suffix property of the CSSCounterStyleRule interface gets and sets the value of the suffix 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 suffix gives us the value ": ".

@counter-style box-corner {
  system: fixed;
  symbols: ◰ ◳ ◲ ◱;
  suffix: ": ";
  negative: "-";
}

let myRules = document.styleSheets[0].cssRules;
console.log(myRules[0].suffix); // ": "