CSSPageRule.selectorText

The selectorText property of the CSSPageRule interface gets and sets the selectors associated with the CSSPageRule.

A CSSOMString.

The stylesheet includes two @page rules. The selectorText property will return the literal selector text of :first as a string.

@page {
  margin: 1cm;
}

@page :first {
  margin: 2cm;
}

let myRules = document.styleSheets[0].cssRules; //returns two myRules
console.log(myRules[1].selectorText); // returns the string ":first"