var defaultEmptyOK = true;
var s_DigitsInPhoneNumber = "10,11";
function isEmpty (s) {
	return ((s == null) || (s.length == 0));
}
function isInteger (s) {
	var i;
	if (isEmpty(s))
		if (isInteger.arguments.length == 1) return defaultEmptyOK;
		else return false;
	for (i = 0; i < s.length; i++) {
		var c = s.charAt(i);
		if (!isDigit(c)) return false;
	}
	return true;
}
function isDigit (c) {
	return ((c >= "0") && (c <= "9"))
}
function isPhoneNumber (s) {
	var isGoodNumber = false;
	if (isEmpty(s)) {
		if (isPhoneNumber.arguments.length == 1) return defaultEmptyOK;
		else return false;
	} else {
		ptnLengthArray = s_DigitsInPhoneNumber.split(",");
		for (i = 0; i<ptnLengthArray.length; i++) {
			if (ptnLengthArray[i] == s.length && isInteger(s)) {
				isGoodNumber = true;
				break;
			}
		}
	}
	return isGoodNumber;
}