Javascript function to check Italian Codice Fiscale

CodiceFiscale.js

function codiceFISCALE(cfins)
	{
		var cf = cfins.toUpperCase();
		var cfReg = /^[A-Z]{6}\d{2}[A-Z]\d{2}[A-Z]\d{3}[A-Z]$/;
		if (!cfReg.test(cf))
		{
			return false;
		}
	  	
		var set1 = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
		var set2 = "ABCDEFGHIJABCDEFGHIJKLMNOPQRSTUVWXYZ";
		var setpari = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
		var setdisp = "BAKPLCQDREVOSFTGUHMINJWZYX";
		var s = 0;
		for( i = 1; i <= 13; i += 2 )
		  s += setpari.indexOf( set2.charAt( set1.indexOf( cf.charAt(i) )));
		for( i = 0; i <= 14; i += 2 )
		  s += setdisp.indexOf( set2.charAt( set1.indexOf( cf.charAt(i) )));
		if ( s%26 != cf.charCodeAt(15)-'A'.charCodeAt(0) )
		  return false;
		return true;
	}

Please note that there are special cases in which the character at position #15 could be a letter. So, this code is not correct.