var digits = "0123456789";

var lowercaseLetters = "abcdefghijklmnopqrstuvwxyz"

var uppercaseLetters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

// whitespace characters
var whitespace = " \t\n\r";

// decimal point character differs by language and culture
var decimalPointDelimiter = "."

// Global variable defaultEmptyOK defines default return value 
// for many functions when they are passed the empty string. 
// By default, they will return defaultEmptyOK.
//
// defaultEmptyOK is false, which means that by default, 
// these functions will do "strict" validation.  Function
// isInteger, for example, will only return true if it is
// passed a string containing an integer; if it is passed
// the empty string, it will return false.
//
// You can change this default behavior globally (for all 
// functions which use defaultEmptyOK) by changing the value
// of defaultEmptyOK.
//
// Most of these functions have an optional argument emptyOK
// which allows you to override the default behavior for 
// the duration of a function call.
//
// This functionality is useful because it is possible to
// say "if the user puts anything in this field, it must
// be an integer (or a phone number, or a string, etc.), 
// but it's OK to leave the field empty too."
// This is the case for fields which are optional but which
// must have a certain kind of content if filled in.

var defaultEmptyOK = false

// Check whether string s is empty.

function isEmpty(s)
{
	return ((s == null) || (s.length == 0))
}

// Returns true if string s is empty or 
// whitespace characters only.

function isWhitespace (s)
{
	var i;

	// Is s empty?
	if (isEmpty(s)) return true;

	// Search through string's characters one by one
	// until we find a non-whitespace character.
	// When we do, return false; if we don't, return true.

	for (i = 0; i < s.length; i++)
	{   
		// Check that current character isn't whitespace.
		var c = s.charAt(i);

		if (whitespace.indexOf(c) == -1) return false;
	}

	// All characters are whitespace.
	return true;
}


// isAlphabetic (STRING s [, BOOLEAN emptyOK])
// 
// Returns true if string s is English letters 
// (A .. Z, a..z) only.
//
// For explanation of optional argument emptyOK,
// see comments of function isInteger.
//
// NOTE: Need i18n version to support European characters.
// This could be tricky due to different character
// sets and orderings for various languages and platforms.

function isAlphabetic (s)

{
	var i;

	if (isEmpty(s)) 
	 if (isAlphabetic.arguments.length == 1) return defaultEmptyOK;
	 else return (isAlphabetic.arguments[1] == true);

	// Search through string's characters one by one
	// until we find a non-alphabetic character.
	// When we do, return false; if we don't, return true.

	for (i = 0; i < s.length; i++)
	{   
		// Check that current character is letter.
		var c = s.charAt(i);

		if (!isLetter(c))
		return false;
	}

	// All characters are letters.
	return true;
}

// isEmail (STRING s [, BOOLEAN emptyOK])
// 
// Email address must be of form a@b.c -- in other words:
// * there must be at least one character before the @
// * there must be at least one character before and after the .
// * the characters @ and . are both required
//
// For explanation of optional argument emptyOK,
// see comments of function isInteger.

function isEmail (s)
{
	if (isEmpty(s)) 
	 if (isEmail.arguments.length == 1) return defaultEmptyOK;
	 else return (isEmail.arguments[1] == true);

	// is s whitespace?
	if (isWhitespace(s)) return false;

	// there must be >= 1 character before @, so we
	// start looking at character position 1 
	// (i.e. second character)
	var i = 1;
	var sLength = s.length;

	// look for @
	while ((i < sLength) && (s.charAt(i) != "@"))
	{ i++
	}

	if ((i >= sLength) || (s.charAt(i) != "@")) return false;
	else i += 2;

	// look for .
	while ((i < sLength) && (s.charAt(i) != "."))
	{ i++
	}

	// there must be at least one character after the .
	if ((i >= sLength - 1) || (s.charAt(i) != ".")) return false;
	else return true;
}