RegExp.lastParen

function matchDemo(){
   var s;                                //Declare variable.
   var re = new RegExp("d(b+)(d)","ig"); //Regular expression pattern.
   var str = "cdbBdbsbdbdz";             //String to be searched.
   var arr = re.exec(str);               //Perform the search.
   s = "$1 returns: " + RegExp.$1 + "\n";
   s += "$2 returns: " + RegExp.$2 + "\n";
   s += "$3 returns: " + RegExp.$3 + "\n";
   s += "input returns : " + RegExp.input + "\n";
   s += "lastMatch returns: " + RegExp.lastMatch + "\n";
   s += "leftContext returns: " + RegExp.leftContext + "\n";
   s += "rightContext returns: " + RegExp.rightContext + "\n"; 
   s += "lastParen returns: " + RegExp.lastParen + "\n";
   return(s);                            //Return results.
}
document.write(matchDemo());