// FormChek.js
//
// SUMMARY
//
// This is a set of JavaScript functions for validating input on 
// an HTML form.  Functions are provided to validate:
//
//      - U.S. and international phone/fax numbers
//      - U.S. ZIP codes (5 or 9 digit postal codes)
//      - U.S. Postal Codes (2 letter abbreviations for names of states)
//      - U.S. Social Security Numbers (abbreviated as SSNs)
//      - email addresses
//	- dates (entry of year, month, and day and validity of combined date)
//	- credit card numbers
//
// Supporting utility functions validate that:
//
//      - characters are Letter, Digit, or LetterOrDigit
//      - strings are a Signed, Positive, Negative, Nonpositive, or
//        Nonnegative integer
//      - strings are a Float or a SignedFloat
//      - strings are Alphabetic, Alphanumeric, or Whitespace
//      - strings contain an integer within a specified range
//
// Functions are also provided to interactively check the
// above kinds of data and jsfc_prompt the user if they have
// been entered incorrectly.
//
// Other utility functions are provided to:
//
// 	- remove from a string characters which are/are not 
//	  in a "bag" of selected characters	
// 	- jsfc_reformat a string, adding delimiter characters
//	- strip whitespace/leading whitespace from a string
//      - jsfc_reformat U.S. phone numbers, ZIP codes, and Social
//        Security numbers
//
//
// Many of the below functions take an optional parameter eok (for "emptyOK")
// which determines whether the empty string will return true or false.
// Default behavior is controlled by global variable defaultEmptyOK.
//
// BASIC DATA VALIDATION FUNCTIONS:
//
// jsfc_isWhitespace (s)                    Check whether string s is empty or whitespace.
// jsfc_isLetter (c)                        Check whether character c is an English letter 
// jsfc_isDigit (c)                         Check whether character c is a digit 
// jsfc_isLetterOrDigit (c)                 Check whether character c is a letter or digit.
// jsfc_isInteger (s [,eok])                True if all characters in string s are numbers.
// jsfc_isSignedInteger (s [,eok])          True if all characters in string s are numbers; leading + or - allowed.
// jsfc_isPositiveInteger (s [,eok])        True if string s is an integer > 0.
// jsfc_isNonnegativeInteger (s [,eok])     True if string s is an integer >= 0.
// jsfc_isNegativeInteger (s [,eok])        True if s is an integer < 0.
// jsfc_isNonpositiveInteger (s [,eok])     True if s is an integer <= 0.
// jsfc_isFloat (s [,eok])                  True if string s is an unsigned floating point (real) number. (Integers also OK.)
// jsfc_isSignedFloat (s [,eok])            True if string s is a floating point number; leading + or - allowed. (Integers also OK.)
// jsfc_isAlphabetic (s [,eok])             True if string s is English letters 
// jsfc_isAlphanumeric (s [,eok])           True if string s is English letters and numbers only.
// 
// jsfc_isSSN (s [,eok])                    True if string s is a valid U.S. Social Security Number.
// jsfc_isUSPhoneNumber (s [,eok])          True if string s is a valid U.S. Phone Number. 
// jsfc_isInternationalPhoneNumber (s [,eok]) True if string s is a valid international phone number.
// jsfc_isZIPCode (s [,eok])                True if string s is a valid U.S. ZIP code.
// jsfc_isStateCode (s [,eok])              True if string s is a valid U.S. Postal Code
// jsfc_isEmail (s [,eok])                  True if string s is a valid email address.
// jsfc_isYear (s [,eok])                   True if string s is a valid Year number.
// jsfc_isIntegerInRange (s, a, b [,eok])   True if string s is an integer between a and b, inclusive.
// jsfc_isMonth (s [,eok])                  True if string s is a valid month between 1 and 12.
// jsfc_isDay (s [,eok])                    True if string s is a valid day between 1 and 31.
// jsfc_daysInFebruary (year)               Returns number of days in February of that year.
// jsfc_isDate (year, month, day)           True if string arguments form a valid date.

// FUNCTIONS TO REFORMAT DATA:
//
// jsfc_stripCharsInBag (s, bag)            Removes all characters in string bag from string s.
// jsfc_stripCharsNotInBag (s, bag)         Removes all characters NOT in string bag from string s.
// jsfc_stripWhitespace (s)                 Removes all whitespace characters from s.
// jsfc_stripInitialWhitespace (s)          Removes initial (leading) whitespace characters from s.
// jsfc_reformat (TARGETSTRING, STRING,     Function for inserting formatting characters or
//   INTEGER, STRING, INTEGER ... )       delimiters into TARGETSTRING.                                       
// jsfc_reformatZIPCode (ZIPString)         If 9 digits, inserts separator hyphen.
// jsfc_reformatSSN (SSN)                   Reformats as 123-45-6789.
// jsfc_reformatUSPhone (USPhone)           Reformats as (123) 456-789.

// FUNCTIONS TO PROMPT USER:
//
// jsfc_prompt (s)                          Display jsfc_prompt string s in status bar.
// jsfc_promptEntry (s)                     Display data entry jsfc_prompt string s in status bar.
// jsfc_warnEmpty (theField, s)             Notify user that required field theField is empty.
// jsfc_warnInvalid (theField, s)           Notify user that contents of field theField are invalid.

// FUNCTIONS TO INTERACTIVELY CHECK FIELD CONTENTS:
//
// jsfc_checkString (theField, s [,eok])    Check that theField.value is not empty or all whitespace.
// jsfc_checkStateCode (theField)           Check that theField.value is a valid U.S. state code.
// jsfc_checkZIPCode (theField [,eok])      Check that theField.value is a valid ZIP code.
// jsfc_checkUSPhone (theField [,eok])      Check that theField.value is a valid US Phone.
// jsfc_checkInternationalPhone (theField [,eok])  Check that theField.value is a valid International Phone.
// jsfc_checkEmail (theField [,eok])        Check that theField.value is a valid Email.
// jsfc_checkSSN (theField [,eok])          Check that theField.value is a valid SSN.
// jsfc_checkYear (theField [,eok])         Check that theField.value is a valid Year.
// jsfc_checkMonth (theField [,eok])        Check that theField.value is a valid Month.
// jsfc_checkDay (theField [,eok])          Check that theField.value is a valid Day.
// jsfc_checkDate (yearField, monthField, dayField, labelString, OKtoOmitDay)
//                                     Check that field values form a valid date.
// jsfc_getRadioButtonValue (radio)         Get checked value from radio button.
// jsfc_checkCreditCard (radio, theField)   Validate credit card info.

// CREDIT CARD DATA VALIDATION FUNCTIONS
// 
// jsfc_isCreditCard (st)              True if credit card number passes the Luhn Mod-10 test.
// jsfc_isVisa (cc)                    True if string cc is a valid VISA number.
// jsfc_isMasterCard (cc)              True if string cc is a valid MasterCard number.
// jsfc_isAmericanExpress (cc)         True if string cc is a valid American Express number.
// jsfc_isDinersClub (cc)              True if string cc is a valid Diner's Club number.
// jsfc_isCarteBlanche (cc)            True if string cc is a valid Carte Blanche number.
// jsfc_isDiscover (cc)                True if string cc is a valid Discover card number.
// jsfc_isEnRoute (cc)                 True if string cc is a valid enRoute card number.
// jsfc_isJCB (cc)                     True if string cc is a valid JCB card number.
// jsfc_isAnyCard (cc)                 True if string cc is a valid card number for any of the accepted types.
// jsfc_isCardMatch (Type, Number)     True if Number is valid for credic card of type Type.
//

// Other stub functions are retained for backward compatibility with LivePayment code.
// See comments below for details.
//
// Performance hint: when you deploy this file on your website, strip out the
// comment lines from the source code as well as any of the functions which
// you don't need.  This will give you a smaller .js file and achieve faster
// downloads.
//
// 18 Feb 97 created Eric Krock
//
// (c) 1997 Netscape Communications Corporation

// VARIABLE DECLARATIONS
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 = "."
// non-digit characters which are allowed in phone numbers
var phoneNumberDelimiters = "()- ";
// characters which are allowed in US phone numbers
var validUSPhoneChars = digits + phoneNumberDelimiters;
// characters which are allowed in international phone numbers
// (a leading + is OK)
var validWorldPhoneChars = digits + phoneNumberDelimiters + "+";
// non-digit characters which are allowed in 
// Social Security Numbers
var SSNDelimiters = "- ";
// characters which are allowed in Social Security Numbers
var validSSNChars = digits + SSNDelimiters;
// U.S. Social Security Numbers have 9 digits.
// They are formatted as 123-45-6789.
var digitsInSocialSecurityNumber = 9;
// U.S. phone numbers have 10 digits.
// They are formatted as 123 456 7890 or (123) 456-7890.
var digitsInUSPhoneNumber = 10;
// non-digit characters which are allowed in ZIP Codes
var ZIPCodeDelimiters = "-";
// our preferred delimiter for reformatting ZIP Codes
var ZIPCodeDelimeter = "-"
// characters which are allowed in Social Security Numbers
var validZIPCodeChars = digits + ZIPCodeDelimiters
// U.S. ZIP codes have 5 or 9 digits.
// They are formatted as 12345 or 12345-6789.
var digitsInZIPCode1 = 5
var digitsInZIPCode2 = 9
// non-digit characters which are allowed in credit card numbers
var creditCardDelimiters = " "

// CONSTANT STRING DECLARATIONS
// (grouped for ease of translation and localization)
// m is an abbreviation for "missing"
var mPrefix = "You did not enter a value into the "
var mSuffix = " field. This is a required field. Please enter it now."
// s is an abbreviation for "string"
var sUSLastName = "Last Name"
var sUSFirstName = "First Name"
var sWorldLastName = "Family Name"
var sWorldFirstName = "Given Name"
var sTitle = "Title"
var sCompanyName = "Company Name"
var sUSAddress = "Street Address"
var sWorldAddress = "Address"
var sCity = "City"
var sStateCode = "State Code"
var sWorldState = "State, Province, or Prefecture"
var sCountry = "Country"
var sZIPCode = "ZIP Code"
var sWorldPostalCode = "Postal Code"
var sPhone = "Phone Number"
var sFax = "Fax Number"
var sDateOfBirth = "Date of Birth"
var sExpirationDate = "Expiration Date"
var sEmail = "Email"
var sSSN = "Social Security Number"
var sCreditCardNumber = "Credit Card Number"
var sOtherInfo = "Other Information"
// i is an abbreviation for "invalid"
var iStateCode = "This field must be a valid two character U.S. state abbreviation (like CA for California). Please reenter it now."
var iZIPCode = "This field must be a 5 or 9 digit U.S. ZIP Code (like 94043). Please reenter it now."
var iUSPhone = "This field must be a 10 digit U.S. phone number (like 415 555 1212). Please reenter it now."
var iWorldPhone = "This field must be a valid international phone number. Please reenter it now."
var iSSN = "This field must be a 9 digit U.S. social security number (like 123 45 6789). Please reenter it now."
var iEmail = "This field must be a valid email address (like foo@bar.com). Please reenter it now."
var iCreditCardPrefix = "This is not a valid "
var iCreditCardSuffix = " credit card number. (Click the link on this form to see a list of sample numbers.) Please reenter it now."
var iDay = "This field must be a day number between 1 and 31.  Please reenter it now."
var iMonth = "This field must be a month number between 1 and 12.  Please reenter it now."
var iYear = "This field must be a 2 or 4 digit year number.  Please reenter it now."
var iDatePrefix = "The Day, Month, and Year for "
var iDateSuffix = " do not form a valid date.  Please reenter them now."
// p is an abbreviation for "jsfc_prompt"
var pEntryPrompt = "Please enter a "
var pStateCode = "2 character code (like CA)."
var pZIPCode = "5 or 9 digit U.S. ZIP Code (like 94043)."
var pUSPhone = "10 digit U.S. phone number (like 415 555 1212)."
var pWorldPhone = "international phone number."
var pSSN = "9 digit U.S. social security number (like 123 45 6789)."
var pEmail = "valid email address (like foo@bar.com)."
var pCreditCard = "valid credit card number."
var pDay = "day number between 1 and 31."
var pMonth = "month number between 1 and 12."
var pYear = "2 or 4 digit year number."

// 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
// jsfc_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

// Attempting to make this library run on Navigator 2.0,
// so I'm supplying this array creation routine as per
// JavaScript 1.0 documentation.  If you're using 
// Navigator 3.0 or later, you don't need to do this;
// you can use the Array constructor instead.
function jsfc_makeArray(n) {
//*** BUG: If I put this line in, I get two error messages:
//(1) Window.length can't be set by assignment
//(2) jsfc_daysInMonth has no property indexed by 4
//If I leave it out, the code works fine.
//   this.length = n;
   for (var i = 1; i <= n; i++) {
      this[i] = 0
   } 
   return this
}

var jsfc_daysInMonth = jsfc_makeArray(12);
jsfc_daysInMonth[1] = 31;
jsfc_daysInMonth[2] = 29;   // must programmatically check this
jsfc_daysInMonth[3] = 31;
jsfc_daysInMonth[4] = 30;
jsfc_daysInMonth[5] = 31;
jsfc_daysInMonth[6] = 30;
jsfc_daysInMonth[7] = 31;
jsfc_daysInMonth[8] = 31;
jsfc_daysInMonth[9] = 30;
jsfc_daysInMonth[10] = 31;
jsfc_daysInMonth[11] = 30;
jsfc_daysInMonth[12] = 31;

// Valid U.S. Postal Codes for states, territories, armed forces, etc.
// See http://www.usps.gov/ncsc/lookups/abbr_state.txt.
var USStateCodeDelimiter = "|";
var USStateCodes = "AL|AK|AS|AZ|AR|CA|CO|CT|DE|DC|FM|FL|GA|GU|HI|ID|IL|IN|IA|KS|KY|LA|ME|MH|MD|MA|MI|MN|MS|MO|MT|NE|NV|NH|NJ|NM|NY|NC|ND|MP|OH|OK|OR|PW|PA|PR|RI|SC|SD|TN|TX|UT|VT|VI|VA|WA|WV|WI|WY|AE|AA|AE|AE|AP"

// Check whether string s is empty.
function jsfc_isEmpty(s)
{   return ((s == null) || (s.length == 0))
}

// Returns true if string s is empty or 
// whitespace characters only.
function jsfc_isWhitespace (s)
{   var i;
    // Is s empty?
    if (jsfc_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;
}

// Removes all characters which appear in string bag from string s.
function jsfc_stripCharsInBag (s, bag)
{   var i;
    var returnString = "";
    // Search through string's characters one by one.
    // If character is not in bag, append to returnString.
    for (i = 0; i < s.length; i++)
    {   
        // Check that current character isn't whitespace.
        var c = s.charAt(i);
        if (bag.indexOf(c) == -1) returnString += c;
    }
    return returnString;
}
// Removes all characters which do NOT appear in string bag 
// from string s.
function jsfc_stripCharsNotInBag (s, bag)
{   var i;
    var returnString = "";
    // Search through string's characters one by one.
    // If character is in bag, append to returnString.
    for (i = 0; i < s.length; i++)
    {   
        // Check that current character isn't whitespace.
        var c = s.charAt(i);
        if (bag.indexOf(c) != -1) returnString += c;
    }
    return returnString;
}

// Removes all whitespace characters from s.
// Global variable whitespace (see above)
// defines which characters are considered whitespace.
function jsfc_stripWhitespace (s)
{   return jsfc_stripCharsInBag (s, whitespace)
}

// WORKAROUND FUNCTION FOR NAVIGATOR 2.0.2 COMPATIBILITY.
//
// The below function *should* be unnecessary.  In general,
// avoid using it.  Use the standard method indexOf instead.
//
// However, because of an apparent bug in indexOf on 
// Navigator 2.0.2, the below loop does not work as the
// body of jsfc_stripInitialWhitespace:
//
// while ((i < s.length) && (whitespace.indexOf(s.charAt(i)) != -1))
//   i++;
//
// ... so we provide this workaround function charInString
// instead.
//
// charInString (CHARACTER c, STRING s)
//
// Returns true if single character c (actually a string)
// is contained within string s.
function charInString (c, s)
{   for (i = 0; i < s.length; i++)
    {   if (s.charAt(i) == c) return true;
    }
    return false
}

// Removes initial (leading) whitespace characters from s.
// Global variable whitespace (see above)
// defines which characters are considered whitespace.
function jsfc_stripInitialWhitespace (s)
{   var i = 0;
    while ((i < s.length) && charInString (s.charAt(i), whitespace))
       i++;
    return s.substring (i, s.length);
}

// Returns true if character c is an English letter 
// (A .. Z, a..z).
//
// 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 jsfc_isLetter (c)
{   return ( ((c >= "a") && (c <= "z")) || ((c >= "A") && (c <= "Z")) )
}

// Returns true if character c is a digit 
// (0 .. 9).
function jsfc_isDigit (c)
{   return ((c >= "0") && (c <= "9"))
}

// Returns true if character c is a letter or digit.
function jsfc_isLetterOrDigit (c)
{   return (jsfc_isLetter(c) || jsfc_isDigit(c))
}

// jsfc_isInteger (STRING s [, BOOLEAN emptyOK])
// 
// Returns true if all characters in string s are numbers.
//
// Accepts non-signed integers only. Does not accept floating 
// point, exponential notation, etc.
//
// We don't use parseInt because that would accept a string
// with trailing non-numeric characters.
//
// By default, returns defaultEmptyOK if s is empty.
// There is an optional second argument called emptyOK.
// emptyOK is used to override for a single function call
//      the default behavior which is specified globally by
//      defaultEmptyOK.
// If emptyOK is false (or any value other than true), 
//      the function will return false if s is empty.
// If emptyOK is true, the function will return true if s is empty.
//
// EXAMPLE FUNCTION CALL:     RESULT:
// jsfc_isInteger ("5")            true 
// jsfc_isInteger ("")             defaultEmptyOK
// jsfc_isInteger ("-5")           false
// jsfc_isInteger ("", true)       true
// jsfc_isInteger ("", false)      false
// jsfc_isInteger ("5", false)     true
function jsfc_isInteger (s)
{   var i;
    if (jsfc_isEmpty(s)) 
       if (jsfc_isInteger.arguments.length == 1) return defaultEmptyOK;
       else return (jsfc_isInteger.arguments[1] == true);
    // Search through string's characters one by one
    // until we find a non-numeric character.
    // When we do, return false; if we don't, return true.
    for (i = 0; i < s.length; i++)
    {   
        // Check that current character is number.
        var c = s.charAt(i);
        if (!jsfc_isDigit(c)) return false;
    }
    // All characters are numbers.
    return true;
}

// jsfc_isSignedInteger (STRING s [, BOOLEAN emptyOK])
// 
// Returns true if all characters are numbers; 
// first character is allowed to be + or - as well.
//
// Does not accept floating point, exponential notation, etc.
//
// We don't use parseInt because that would accept a string
// with trailing non-numeric characters.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
//
// EXAMPLE FUNCTION CALL:          RESULT:
// jsfc_isSignedInteger ("5")           true 
// jsfc_isSignedInteger ("")            defaultEmptyOK
// jsfc_isSignedInteger ("-5")          true
// jsfc_isSignedInteger ("+5")          true
// jsfc_isSignedInteger ("", false)     false
// jsfc_isSignedInteger ("", true)      true
function jsfc_isSignedInteger (s)
{   if (jsfc_isEmpty(s)) 
       if (jsfc_isSignedInteger.arguments.length == 1) return defaultEmptyOK;
       else return (jsfc_isSignedInteger.arguments[1] == true);
    else {
        var startPos = 0;
        var secondArg = defaultEmptyOK;
        if (jsfc_isSignedInteger.arguments.length > 1)
            secondArg = jsfc_isSignedInteger.arguments[1];
        // skip leading + or -
        if ( (s.charAt(0) == "-") || (s.charAt(0) == "+") )
           startPos = 1;    
        return (jsfc_isInteger(s.substring(startPos, s.length), secondArg))
    }
}

// jsfc_isPositiveInteger (STRING s [, BOOLEAN emptyOK])
// 
// Returns true if string s is an integer > 0.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_isPositiveInteger (s)
{   var secondArg = defaultEmptyOK;
    if (jsfc_isPositiveInteger.arguments.length > 1)
        secondArg = jsfc_isPositiveInteger.arguments[1];
    // The next line is a bit byzantine.  What it means is:
    // a) s must be a signed integer, AND
    // b) one of the following must be true:
    //    i)  s is empty and we are supposed to return true for
    //        empty strings
    //    ii) this is a positive, not negative, number
    return (jsfc_isSignedInteger(s, secondArg)
         && ( (jsfc_isEmpty(s) && secondArg)  || (parseInt (s) > 0) ) );
}

// jsfc_isNonnegativeInteger (STRING s [, BOOLEAN emptyOK])
// 
// Returns true if string s is an integer >= 0.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_isNonnegativeInteger (s)
{   var secondArg = defaultEmptyOK;
    if (jsfc_isNonnegativeInteger.arguments.length > 1)
        secondArg = jsfc_isNonnegativeInteger.arguments[1];
    // The next line is a bit byzantine.  What it means is:
    // a) s must be a signed integer, AND
    // b) one of the following must be true:
    //    i)  s is empty and we are supposed to return true for
    //        empty strings
    //    ii) this is a number >= 0
    return (jsfc_isSignedInteger(s, secondArg)
         && ( (jsfc_isEmpty(s) && secondArg)  || (parseInt (s) >= 0) ) );
}

// jsfc_isNegativeInteger (STRING s [, BOOLEAN emptyOK])
// 
// Returns true if string s is an integer < 0.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_isNegativeInteger (s)
{   var secondArg = defaultEmptyOK;
    if (jsfc_isNegativeInteger.arguments.length > 1)
        secondArg = jsfc_isNegativeInteger.arguments[1];
    // The next line is a bit byzantine.  What it means is:
    // a) s must be a signed integer, AND
    // b) one of the following must be true:
    //    i)  s is empty and we are supposed to return true for
    //        empty strings
    //    ii) this is a negative, not positive, number
    return (jsfc_isSignedInteger(s, secondArg)
         && ( (jsfc_isEmpty(s) && secondArg)  || (parseInt (s) < 0) ) );
}

// jsfc_isNonpositiveInteger (STRING s [, BOOLEAN emptyOK])
// 
// Returns true if string s is an integer <= 0.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_isNonpositiveInteger (s)
{   var secondArg = defaultEmptyOK;
    if (jsfc_isNonpositiveInteger.arguments.length > 1)
        secondArg = jsfc_isNonpositiveInteger.arguments[1];
    // The next line is a bit byzantine.  What it means is:
    // a) s must be a signed integer, AND
    // b) one of the following must be true:
    //    i)  s is empty and we are supposed to return true for
    //        empty strings
    //    ii) this is a number <= 0
    return (jsfc_isSignedInteger(s, secondArg)
         && ( (jsfc_isEmpty(s) && secondArg)  || (parseInt (s) <= 0) ) );
}

// jsfc_isFloat (STRING s [, BOOLEAN emptyOK])
// 
// True if string s is an unsigned floating point (real) number. 
//
// Also returns true for unsigned integers. If you wish
// to distinguish between integers and floating point numbers,
// first call jsfc_isInteger, then call jsfc_isFloat.
//
// Does not accept exponential notation.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_isFloat (s)
{   var i;
    var seenDecimalPoint = false;
    if (jsfc_isEmpty(s)) 
       if (jsfc_isFloat.arguments.length == 1) return defaultEmptyOK;
       else return (jsfc_isFloat.arguments[1] == true);
    if (s == decimalPointDelimiter) return false;
    // Search through string's characters one by one
    // until we find a non-numeric character.
    // When we do, return false; if we don't, return true.
    for (i = 0; i < s.length; i++)
    {   
        // Check that current character is number.
        var c = s.charAt(i);
        if ((c == decimalPointDelimiter) && !seenDecimalPoint) seenDecimalPoint = true;
        else if (!jsfc_isDigit(c)) return false;
    }
    // All characters are numbers.
    return true;
}

// jsfc_isSignedFloat (STRING s [, BOOLEAN emptyOK])
// 
// True if string s is a signed or unsigned floating point 
// (real) number. First character is allowed to be + or -.
//
// Also returns true for unsigned integers. If you wish
// to distinguish between integers and floating point numbers,
// first call jsfc_isSignedInteger, then call jsfc_isSignedFloat.
//
// Does not accept exponential notation.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_isSignedFloat (s)
{   if (jsfc_isEmpty(s)) 
       if (jsfc_isSignedFloat.arguments.length == 1) return defaultEmptyOK;
       else return (jsfc_isSignedFloat.arguments[1] == true);
    else {
        var startPos = 0;
        var secondArg = defaultEmptyOK;
        if (jsfc_isSignedFloat.arguments.length > 1)
            secondArg = jsfc_isSignedFloat.arguments[1];
        // skip leading + or -
        if ( (s.charAt(0) == "-") || (s.charAt(0) == "+") )
           startPos = 1;    
        return (jsfc_isFloat(s.substring(startPos, s.length), secondArg))
    }
}

// jsfc_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 jsfc_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 jsfc_isAlphabetic (s)
{   var i;
    if (jsfc_isEmpty(s)) 
       if (jsfc_isAlphabetic.arguments.length == 1) return defaultEmptyOK;
       else return (jsfc_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 (!jsfc_isLetter(c))
        return false;
    }
    // All characters are letters.
    return true;
}

// jsfc_isAlphanumeric (STRING s [, BOOLEAN emptyOK])
// 
// Returns true if string s is English letters 
// (A .. Z, a..z) and numbers only.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_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 jsfc_isAlphanumeric (s)
{   var i;
    if (jsfc_isEmpty(s)) 
       if (jsfc_isAlphanumeric.arguments.length == 1) return defaultEmptyOK;
       else return (jsfc_isAlphanumeric.arguments[1] == true);
    // Search through string's characters one by one
    // until we find a non-alphanumeric character.
    // When we do, return false; if we don't, return true.
    for (i = 0; i < s.length; i++)
    {   
        // Check that current character is number or letter.
        var c = s.charAt(i);
        if (! (jsfc_isLetter(c) || jsfc_isDigit(c) ) )
        return false;
    }
    // All characters are numbers or letters.
    return true;
}

// jsfc_reformat (TARGETSTRING, STRING, INTEGER, STRING, INTEGER ... )       
//
// Handy function for arbitrarily inserting formatting characters
// or delimiters of various kinds within TARGETSTRING.
//
// jsfc_reformat takes one named argument, a string s, and any number
// of other arguments.  The other arguments must be integers or
// strings.  These other arguments specify how string s is to be
// reformatted and how and where other strings are to be inserted
// into it.
//
// jsfc_reformat processes the other arguments in order one by one.
// * If the argument is an integer, jsfc_reformat appends that number 
//   of sequential characters from s to the resultString.
// * If the argument is a string, jsfc_reformat appends the string
//   to the resultString.
//
// NOTE: The first argument after TARGETSTRING must be a string.
// (It can be empty.)  The second argument must be an integer.
// Thereafter, integers and strings must alternate.  This is to
// provide backward compatibility to Navigator 2.0.2 JavaScript
// by avoiding use of the typeof operator.
//
// It is the caller's responsibility to make sure that we do not
// try to copy more characters from s than s.length.
//
// EXAMPLES:
//
// * To jsfc_reformat a 10-digit U.S. phone number from "1234567890"
//   to "(123) 456-7890" make this function call:
//   jsfc_reformat("1234567890", "(", 3, ") ", 3, "-", 4)
//
// * To jsfc_reformat a 9-digit U.S. Social Security number from
//   "123456789" to "123-45-6789" make this function call:
//   jsfc_reformat("123456789", "", 3, "-", 2, "-", 4)
//
// HINT:
//
// If you have a string which is already delimited in one way
// (example: a phone number delimited with spaces as "123 456 7890")
// and you want to delimit it in another way using function jsfc_reformat,
// call function jsfc_stripCharsNotInBag to remove the unwanted 
// characters, THEN call function jsfc_reformat to delimit as desired.
//
// EXAMPLE:
//
// jsfc_reformat (jsfc_stripCharsNotInBag ("123 456 7890", digits),
//           "(", 3, ") ", 3, "-", 4)
function jsfc_reformat (s)
{   var arg;
    var sPos = 0;
    var resultString = "";
    for (var i = 1; i < jsfc_reformat.arguments.length; i++) {
       arg = jsfc_reformat.arguments[i];
       if (i % 2 == 1) resultString += arg;
       else {
           resultString += s.substring(sPos, sPos + arg);
           sPos += arg;
       }
    }
    return resultString;
}

// jsfc_isSSN (STRING s [, BOOLEAN emptyOK])
// 
// jsfc_isSSN returns true if string s is a valid U.S. Social
// Security Number.  Must be 9 digits.
//
// NOTE: Strip out any delimiters (spaces, hyphens, etc.)
// from string s before calling this function.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_isSSN (s)
{   if (jsfc_isEmpty(s)) 
       if (jsfc_isSSN.arguments.length == 1) return defaultEmptyOK;
       else return (jsfc_isSSN.arguments[1] == true);
    return (jsfc_isInteger(s) && s.length == digitsInSocialSecurityNumber)
}

// jsfc_isUSPhoneNumber (STRING s [, BOOLEAN emptyOK])
// 
// jsfc_isUSPhoneNumber returns true if string s is a valid U.S. Phone
// Number.  Must be 10 digits.
//
// NOTE: Strip out any delimiters (spaces, hyphens, parentheses, etc.)
// from string s before calling this function.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_isUSPhoneNumber (s)
{   if (jsfc_isEmpty(s)) 
       if (jsfc_isUSPhoneNumber.arguments.length == 1) return defaultEmptyOK;
       else return (jsfc_isUSPhoneNumber.arguments[1] == true);
    return (jsfc_isInteger(s) && s.length == digitsInUSPhoneNumber)
}

// jsfc_isInternationalPhoneNumber (STRING s [, BOOLEAN emptyOK])
// 
// jsfc_isInternationalPhoneNumber returns true if string s is a valid 
// international phone number.  Must be digits only; any length OK.
// May be prefixed by + character.
//
// NOTE: A phone number of all zeros would not be accepted.
// I don't think that is a valid phone number anyway.
//
// NOTE: Strip out any delimiters (spaces, hyphens, parentheses, etc.)
// from string s before calling this function.  You may leave in 
// leading + character if you wish.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_isInternationalPhoneNumber (s)
{   if (jsfc_isEmpty(s)) 
       if (jsfc_isInternationalPhoneNumber.arguments.length == 1) return defaultEmptyOK;
       else return (jsfc_isInternationalPhoneNumber.arguments[1] == true);
    return (jsfc_isPositiveInteger(s))
}

// jsfc_isZIPCode (STRING s [, BOOLEAN emptyOK])
// 
// jsfc_isZIPCode returns true if string s is a valid 
// U.S. ZIP code.  Must be 5 or 9 digits only.
//
// NOTE: Strip out any delimiters (spaces, hyphens, etc.)
// from string s before calling this function.  
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_isZIPCode (s)
{  if (jsfc_isEmpty(s)) 
       if (jsfc_isZIPCode.arguments.length == 1) return defaultEmptyOK;
       else return (jsfc_isZIPCode.arguments[1] == true);
   return (jsfc_isInteger(s) && 
            ((s.length == digitsInZIPCode1) ||
             (s.length == digitsInZIPCode2)))
}

// jsfc_isStateCode (STRING s [, BOOLEAN emptyOK])
// 
// Return true if s is a valid U.S. Postal Code 
// (abbreviation for state).
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_isStateCode(s)
{   if (jsfc_isEmpty(s)) 
       if (jsfc_isStateCode.arguments.length == 1) return defaultEmptyOK;
       else return (jsfc_isStateCode.arguments[1] == true);
    return ( (USStateCodes.indexOf(s) != -1) &&
             (s.indexOf(USStateCodeDelimiter) == -1) )
}

// jsfc_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 jsfc_isInteger.
function jsfc_isEmail (s)
{   if (jsfc_isEmpty(s)) 
       if (jsfc_isEmail.arguments.length == 1) return defaultEmptyOK;
       else return (jsfc_isEmail.arguments[1] == true);
    // is s whitespace?
    if (jsfc_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;
}

// jsfc_isYear (STRING s [, BOOLEAN emptyOK])
// 
// jsfc_isYear returns true if string s is a valid 
// Year number.  Must be 2 or 4 digits only.
// 
// For Year 2000 compliance, you are advised
// to use 4-digit year numbers everywhere.
//
// And yes, this function is not Year 10000 compliant, but 
// because I am giving you 8003 years of advance notice,
// I don't feel very guilty about this ...
//
// For B.C. compliance, write your own function. ;->
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_isYear (s)
{   if (jsfc_isEmpty(s)) 
       if (jsfc_isYear.arguments.length == 1) return defaultEmptyOK;
       else return (jsfc_isYear.arguments[1] == true);
    if (!jsfc_isNonnegativeInteger(s)) return false;
    return ((s.length == 2) || (s.length == 4));
}

// jsfc_isIntegerInRange (STRING s, INTEGER a, INTEGER b [, BOOLEAN emptyOK])
// 
// jsfc_isIntegerInRange returns true if string s is an integer 
// within the range of integer arguments a and b, inclusive.
// 
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.

function jsfc_isIntegerInRange (s, a, b)
{   if (jsfc_isEmpty(s)) 
       if (jsfc_isIntegerInRange.arguments.length == 1) return defaultEmptyOK;
       else return (jsfc_isIntegerInRange.arguments[1] == true);
    // Catch non-integer strings to avoid creating a NaN below,
    // which isn't available on JavaScript 1.0 for Windows.
    if (!jsfc_isInteger(s, false)) return false;
    // Now, explicitly change the type to integer via parseInt
    // so that the comparison code below will work both on 
    // JavaScript 1.2 (which typechecks in equality comparisons)
    // and JavaScript 1.1 and before (which doesn't).
    var num = parseInt (s);
    return ((num >= a) && (num <= b));
}

// jsfc_isMonth (STRING s [, BOOLEAN emptyOK])
// 
// jsfc_isMonth returns true if string s is a valid 
// month number between 1 and 12.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_isMonth (s)
{   if (jsfc_isEmpty(s)) 
       if (jsfc_isMonth.arguments.length == 1) return defaultEmptyOK;
       else return (jsfc_isMonth.arguments[1] == true);
    return jsfc_isIntegerInRange (s, 1, 12);
}

// jsfc_isDay (STRING s [, BOOLEAN emptyOK])
// 
// jsfc_isDay returns true if string s is a valid 
// day number between 1 and 31.
// 
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_isDay (s)
{   if (jsfc_isEmpty(s)) 
       if (jsfc_isDay.arguments.length == 1) return defaultEmptyOK;
       else return (jsfc_isDay.arguments[1] == true);   
    return jsfc_isIntegerInRange (s, 1, 31);
}

// jsfc_daysInFebruary (INTEGER year)
// 
// Given integer argument year,
// returns number of days in February of that year.

function jsfc_daysInFebruary (year)
{   // February has 29 days in any year evenly divisible by four,
    // EXCEPT for centurial years which are not also divisible by 400.
    return (  ((year % 4 == 0) && ( (!(year % 100 == 0)) || (year % 400 == 0) ) ) ? 29 : 28 );
}

// jsfc_isDate (STRING year, STRING month, STRING day)
//
// jsfc_isDate returns true if string arguments year, month, and day 
// form a valid date.
// 
function jsfc_isDate (year, month, day)
{   // catch invalid years (not 2- or 4-digit) and invalid months and days.
    if (! (jsfc_isYear(year, false) && jsfc_isMonth(month, false) && jsfc_isDay(day, false))) return false;
    // Explicitly change type to integer to make code work in both
    // JavaScript 1.1 and JavaScript 1.2.
    var intYear = parseInt(year);
    var intMonth = parseInt(month);
    var intDay = parseInt(day);
    // catch invalid days, except for February
    if (intDay > jsfc_daysInMonth[intMonth]) return false; 
    if ((intMonth == 2) && (intDay > jsfc_daysInFebruary(intYear))) return false;
    return true;
}

/* FUNCTIONS TO NOTIFY USER OF INPUT REQUIREMENTS OR MISTAKES. */
// Display jsfc_prompt string s in status bar.
function jsfc_prompt (s)
{   window.status = s
}

// Display data entry jsfc_prompt string s in status bar.
function jsfc_promptEntry (s)
{   window.status = pEntryPrompt + s
}

// Notify user that required field theField is empty.
// String s describes expected contents of theField.value.
// Put focus in theField and return false.
function jsfc_warnEmpty (theField, s)
{   theField.focus()
    alert(mPrefix + s + mSuffix)
    return false
}

// Notify user that contents of field theField are invalid.
// String s describes expected contents of theField.value.
// Put select theField, pu focus in it, and return false.
function jsfc_warnInvalid (theField, s)
{   theField.focus()
    theField.select()
    alert(s)
    return false
}

/* FUNCTIONS TO INTERACTIVELY CHECK VARIOUS FIELDS. */
// jsfc_checkString (TEXTFIELD theField, STRING s, [, BOOLEAN emptyOK==false])
//
// Check that string theField.value is not all whitespace.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.

function jsfc_checkString (theField, s, emptyOK)
{   // Next line is needed on NN3 to avoid "undefined is not a number" error
    // in equality comparison below.
    if (jsfc_checkString.arguments.length == 2) emptyOK = defaultEmptyOK;
    if ((emptyOK == true) && (jsfc_isEmpty(theField.value))) return true;
    if (jsfc_isWhitespace(theField.value)) 
       return jsfc_warnEmpty (theField, s);
    else return true;
}

// jsfc_checkStateCode (TEXTFIELD theField [, BOOLEAN emptyOK==false])
//
// Check that string theField.value is a valid U.S. state code.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_checkStateCode (theField, emptyOK)
{   if (jsfc_checkStateCode.arguments.length == 1) emptyOK = defaultEmptyOK;
    if ((emptyOK == true) && (jsfc_isEmpty(theField.value))) return true;
    else
    {  theField.value = theField.value.toUpperCase();
       if (!jsfc_isStateCode(theField.value, false)) 
          return jsfc_warnInvalid (theField, iStateCode);
       else return true;
    }
}

// takes ZIPString, a string of 5 or 9 digits;
// if 9 digits, inserts separator hyphen
function jsfc_reformatZIPCode (ZIPString)
{   if (ZIPString.length == 5) return ZIPString;
    else return (jsfc_reformat (ZIPString, "", 5, "-", 4));
}

// jsfc_checkZIPCode (TEXTFIELD theField [, BOOLEAN emptyOK==false])
//
// Check that string theField.value is a valid ZIP code.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.

function jsfc_checkZIPCode (theField, emptyOK)
{   if (jsfc_checkZIPCode.arguments.length == 1) emptyOK = defaultEmptyOK;
    if ((emptyOK == true) && (jsfc_isEmpty(theField.value))) return true;
    else
    { var normalizedZIP = jsfc_stripCharsInBag(theField.value, ZIPCodeDelimiters)
      if (!jsfc_isZIPCode(normalizedZIP, false)) 
         return jsfc_warnInvalid (theField, iZIPCode);
      else 
      {  // if you don't want to insert a hyphen, comment next line out
         theField.value = jsfc_reformatZIPCode(normalizedZIP)
         return true;
      }
    }
}
// takes USPhone, a string of 10 digits
// and reformats as (123) 456-789
function jsfc_reformatUSPhone (USPhone)
{   return (jsfc_reformat (USPhone, "(", 3, ") ", 3, "-", 4))
}

// jsfc_checkUSPhone (TEXTFIELD theField [, BOOLEAN emptyOK==false])
//
// Check that string theField.value is a valid US Phone.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_checkUSPhone (theField, emptyOK)
{   if (jsfc_checkUSPhone.arguments.length == 1) emptyOK = defaultEmptyOK;
    if ((emptyOK == true) && (jsfc_isEmpty(theField.value))) return true;
    else
    {  var normalizedPhone = jsfc_stripCharsInBag(theField.value, phoneNumberDelimiters)
       if (!jsfc_isUSPhoneNumber(normalizedPhone, false)) 
          return jsfc_warnInvalid (theField, iUSPhone);
       else 
       {  // if you don't want to jsfc_reformat as (123) 456-789, comment next line out
          theField.value = jsfc_reformatUSPhone(normalizedPhone)
          return true;
       }
    }
}

// jsfc_checkInternationalPhone (TEXTFIELD theField [, BOOLEAN emptyOK==false])
//
// Check that string theField.value is a valid International Phone.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_checkInternationalPhone (theField, emptyOK)
{   if (jsfc_checkInternationalPhone.arguments.length == 1) emptyOK = defaultEmptyOK;
    if ((emptyOK == true) && (jsfc_isEmpty(theField.value))) return true;
    else
    {  if (!jsfc_isInternationalPhoneNumber(theField.value, false)) 
          return jsfc_warnInvalid (theField, iWorldPhone);
       else return true;
    }
}

// jsfc_checkEmail (TEXTFIELD theField [, BOOLEAN emptyOK==false])
//
// Check that string theField.value is a valid Email.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.

function jsfc_checkEmail (theField, emptyOK)
{   if (jsfc_checkEmail.arguments.length == 1) emptyOK = defaultEmptyOK;
    if ((emptyOK == true) && (jsfc_isEmpty(theField.value))) return true;
    else if (!jsfc_isEmail(theField.value, false)) 
       return jsfc_warnInvalid (theField, iEmail);
    else return true;
}

// takes SSN, a string of 9 digits
// and reformats as 123-45-6789
function jsfc_reformatSSN (SSN)
{   return (jsfc_reformat (SSN, "", 3, "-", 2, "-", 4))
}

// Check that string theField.value is a valid SSN.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_checkSSN (theField, emptyOK)
{   if (jsfc_checkSSN.arguments.length == 1) emptyOK = defaultEmptyOK;
    if ((emptyOK == true) && (jsfc_isEmpty(theField.value))) return true;
    else
    {  var normalizedSSN = jsfc_stripCharsInBag(theField.value, SSNDelimiters)
       if (!jsfc_isSSN(normalizedSSN, false)) 
          return jsfc_warnInvalid (theField, iSSN);
       else 
       {  // if you don't want to reformats as 123-456-7890, comment next line out
          theField.value = jsfc_reformatSSN(normalizedSSN)
          return true;
       }
    }
}

// Check that string theField.value is a valid Year.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_checkYear (theField, emptyOK)
{   if (jsfc_checkYear.arguments.length == 1) emptyOK = defaultEmptyOK;
    if ((emptyOK == true) && (jsfc_isEmpty(theField.value))) return true;
    if (!jsfc_isYear(theField.value, false)) 
       return jsfc_warnInvalid (theField, iYear);
    else return true;
}

// Check that string theField.value is a valid Month.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_checkMonth (theField, emptyOK)
{   if (jsfc_checkMonth.arguments.length == 1) emptyOK = defaultEmptyOK;
    if ((emptyOK == true) && (jsfc_isEmpty(theField.value))) return true;
    if (!jsfc_isMonth(theField.value, false)) 
       return jsfc_warnInvalid (theField, iMonth);
    else return true;
}

// Check that string theField.value is a valid Day.
//
// For explanation of optional argument emptyOK,
// see comments of function jsfc_isInteger.
function jsfc_checkDay (theField, emptyOK)
{   if (jsfc_checkDay.arguments.length == 1) emptyOK = defaultEmptyOK;
    if ((emptyOK == true) && (jsfc_isEmpty(theField.value))) return true;
    if (!jsfc_isDay(theField.value, false)) 
       return jsfc_warnInvalid (theField, iDay);
    else return true;
}

// jsfc_checkDate (yearField, monthField, dayField, STRING labelString [, OKtoOmitDay==false])
//
// Check that yearField.value, monthField.value, and dayField.value 
// form a valid date.
//
// If they don't, labelString (the name of the date, like "Birth Date")
// is displayed to tell the user which date field is invalid.
//
// If it is OK for the day field to be empty, set optional argument
// OKtoOmitDay to true.  It defaults to false.
function jsfc_checkDate (yearField, monthField, dayField, labelString, OKtoOmitDay)
{   // Next line is needed on NN3 to avoid "undefined is not a number" error
    // in equality comparison below.
    if (jsfc_checkDate.arguments.length == 4) OKtoOmitDay = false;
    if (!jsfc_isYear(yearField.value)) return jsfc_warnInvalid (yearField, iYear);
    if (!jsfc_isMonth(monthField.value)) return jsfc_warnInvalid (monthField, iMonth);
    if ( (OKtoOmitDay == true) && jsfc_isEmpty(dayField.value) ) return true;
    else if (!jsfc_isDay(dayField.value)) 
       return jsfc_warnInvalid (dayField, iDay);
    if (jsfc_isDate (yearField.value, monthField.value, dayField.value))
       return true;
    alert (iDatePrefix + labelString + iDateSuffix)
    return false
}

// Get checked value from radio button.
function jsfc_getRadioButtonValue (radio)
{   for (var i = 0; i < radio.length; i++)
    {   if (radio[i].checked) { break }
    }
    return radio[i].value
}

// Validate credit card info.
function jsfc_checkCreditCard (radio, theField)
{   var cardType = jsfc_getRadioButtonValue (radio)
    var normalizedCCN = jsfc_stripCharsInBag(theField.value, creditCardDelimiters)
    if (!jsfc_isCardMatch(cardType, normalizedCCN)) 
       return jsfc_warnInvalid (theField, iCreditCardPrefix + cardType + iCreditCardSuffix);
    else 
    {  theField.value = normalizedCCN
       return true
    }
}

/*  ================================================================
    Credit card verification functions
    Originally included as Starter Application 1.0.0 in LivePayment.
    20 Feb 1997 modified by egk:
           changed naming convention to initial lowercase
                  (jsfc_isMasterCard instead of IsMasterCard, etc.)
           changed isCC to jsfc_isCreditCard
           retained functions named with older conventions from
                  LivePayment as stub functions for backward 
                  compatibility only
           added "AMERICANEXPRESS" as equivalent of "AMEX" 
                  for naming consistency 
    ================================================================ */

/*  ================================================================
    FUNCTION:  jsfc_isCreditCard(st)

    INPUT:     st - a string representing a credit card number

    RETURNS:  true, if the credit card number passes the Luhn Mod-10
		    test.
	      false, otherwise
    ================================================================ */
function jsfc_isCreditCard(st) {
  // Encoding only works on cards with less than 19 digits
  if (st.length > 19)
    return (false);
  sum = 0; mul = 1; l = st.length;
  for (i = 0; i < l; i++) {
    digit = st.substring(l-i-1,l-i);
    tproduct = parseInt(digit ,10)*mul;
    if (tproduct >= 10)
      sum += (tproduct % 10) + 1;
    else
      sum += tproduct;
    if (mul == 1)
      mul++;
    else
      mul--;
  }

// Uncomment the following line to help create credit card numbers
// 1. Create a dummy number with a 0 as the last digit
// 2. Examine the sum written out
// 3. Replace the last digit with the difference between the sum and
//    the next multiple of 10.

//  document.writeln("<BR>Sum      = ",sum,"<BR>");
//  alert("Sum      = " + sum);
  if ((sum % 10) == 0)
    return (true);
  else
    return (false);
} // END FUNCTION jsfc_isCreditCard()

/*  ================================================================
    FUNCTION:  jsfc_isVisa()
 
    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is a valid VISA number.
       false, otherwise
    Sample number: 4111 1111 1111 1111 (16 digits)
    ================================================================ */
function jsfc_isVisa(cc)
{
  if (((cc.length == 16) || (cc.length == 13)) &&
      (cc.substring(0,1) == 4))
    return jsfc_isCreditCard(cc);
  return false;
}  // END FUNCTION jsfc_isVisa()

/*  ================================================================
    FUNCTION:  jsfc_isMasterCard()

    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is a valid MasterCard
		    number.
	      false, otherwise
    Sample number: 5500 0000 0000 0004 (16 digits)
    ================================================================ */
function jsfc_isMasterCard(cc)
{
  firstdig = cc.substring(0,1);
  seconddig = cc.substring(1,2);
  if ((cc.length == 16) && (firstdig == 5) &&
      ((seconddig >= 1) && (seconddig <= 5)))
    return jsfc_isCreditCard(cc);
  return false;
} // END FUNCTION jsfc_isMasterCard()

/*  ================================================================
    FUNCTION:  jsfc_isAmericanExpress()

    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is a valid American
		    Express number.
	      false, otherwise
    Sample number: 340000000000009 (15 digits)
    ================================================================ */
function jsfc_isAmericanExpress(cc)
{
  firstdig = cc.substring(0,1);
  seconddig = cc.substring(1,2);
  if ((cc.length == 15) && (firstdig == 3) &&
      ((seconddig == 4) || (seconddig == 7)))
    return jsfc_isCreditCard(cc);
  return false;
} // END FUNCTION jsfc_isAmericanExpress()

/*  ================================================================
    FUNCTION:  jsfc_isDinersClub()

    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is a valid Diner's
		    Club number.
	      false, otherwise
    Sample number: 30000000000004 (14 digits)
    ================================================================ */
function jsfc_isDinersClub(cc)
{
  firstdig = cc.substring(0,1);
  seconddig = cc.substring(1,2);
  if ((cc.length == 14) && (firstdig == 3) &&
      ((seconddig == 0) || (seconddig == 6) || (seconddig == 8)))
   return jsfc_isCreditCard(cc);
  return false;
}

/*  ================================================================
    FUNCTION:  jsfc_isCarteBlanche()
 
    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is a valid Carte
		    Blanche number.
	      false, otherwise
    ================================================================ */
function jsfc_isCarteBlanche(cc)
{
  return jsfc_isDinersClub(cc);
}

/*  ================================================================
    FUNCTION:  jsfc_isDiscover()
 
    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is a valid Discover
		    card number.
	      false, otherwise
    Sample number: 6011000000000004 (16 digits)
    ================================================================ */
function jsfc_isDiscover(cc)
{
  first4digs = cc.substring(0,4);
  if ((cc.length == 16) && (first4digs == "6011"))
    return jsfc_isCreditCard(cc);
  return false;
} // END FUNCTION jsfc_isDiscover()

/*  ================================================================
    FUNCTION:  jsfc_isEnRoute()

    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is a valid enRoute
		    card number.
	      false, otherwise
    Sample number: 201400000000009 (15 digits)
    ================================================================ */
function jsfc_isEnRoute(cc)
{
  first4digs = cc.substring(0,4);
  if ((cc.length == 15) &&
      ((first4digs == "2014") ||
       (first4digs == "2149")))
    return jsfc_isCreditCard(cc);
  return false;
}

/*  ================================================================
    FUNCTION:  jsfc_isJCB()
 
    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is a valid JCB
		    card number.
	      false, otherwise
    ================================================================ */
function jsfc_isJCB(cc)
{
  first4digs = cc.substring(0,4);
  if ((cc.length == 16) &&
      ((first4digs == "3088") ||
       (first4digs == "3096") ||
       (first4digs == "3112") ||
       (first4digs == "3158") ||
       (first4digs == "3337") ||
       (first4digs == "3528")))
    return jsfc_isCreditCard(cc);
  return false;
} // END FUNCTION jsfc_isJCB()

/*  ================================================================
    FUNCTION:  jsfc_isAnyCard()

    INPUT:     cc - a string representing a credit card number

    RETURNS:  true, if the credit card number is any valid credit
		    card number for any of the accepted card types.
	      false, otherwise
    ================================================================ */
function jsfc_isAnyCard(cc)
{
  if (!jsfc_isCreditCard(cc))
    return false;
  if (!jsfc_isMasterCard(cc) && !jsfc_isVisa(cc) && !jsfc_isAmericanExpress(cc) && !jsfc_isDinersClub(cc) &&
      !jsfc_isDiscover(cc) && !jsfc_isEnRoute(cc) && !jsfc_isJCB(cc)) {
    return false;
  }
  return true;
} // END FUNCTION jsfc_isAnyCard()

/*  ================================================================
    FUNCTION:  jsfc_isCardMatch()
    INPUT:    cardType - a string representing the credit card type
       cardNumber - a string representing a credit card number
    RETURNS:  true, if the credit card number is valid for the particular
	      credit card type given in "cardType".
	      false, otherwise
    ================================================================ */
function jsfc_isCardMatch (cardType, cardNumber)
{
	cardType = cardType.toUpperCase();
	var doesMatch = true;
	if ((cardType == "VISA") && (!jsfc_isVisa(cardNumber)))
		doesMatch = false;
	if ((cardType == "MASTERCARD") && (!jsfc_isMasterCard(cardNumber)))
		doesMatch = false;
	if ( ( (cardType == "AMERICANEXPRESS") || (cardType == "AMEX") )
                && (!jsfc_isAmericanExpress(cardNumber))) doesMatch = false;
	if ((cardType == "DISCOVER") && (!jsfc_isDiscover(cardNumber)))
		doesMatch = false;
	if ((cardType == "JCB") && (!jsfc_isJCB(cardNumber)))
		doesMatch = false;
	if ((cardType == "DINERS") && (!jsfc_isDinersClub(cardNumber)))
		doesMatch = false;
	if ((cardType == "CARTEBLANCHE") && (!jsfc_isCarteBlanche(cardNumber)))
		doesMatch = false;
	if ((cardType == "ENROUTE") && (!jsfc_isEnRoute(cardNumber)))
		doesMatch = false;
	return doesMatch;
}  // END FUNCTION CardMatch()