// 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)
//      - email addresses
//	- dates (entry of year, month, and day and validity of combined date)
//
// 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 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	
// 	- reformat a string, adding delimiter characters
//	- strip whitespace/leading whitespace from a string
//      - reformat U.S. phone numbers, ZIP codes
//
//
// 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:
//
// isWhitespace (s)                    Check whether string s is empty or whitespace.
// isLetter (c)                        Check whether character c is an English letter 
// isDigit (c)                         Check whether character c is a digit 
// isLetterOrDigit (c)                 Check whether character c is a letter or digit.
// isInteger (s [,eok])                True if all characters in string s are numbers.
// isSignedInteger (s [,eok])          True if all characters in string s are numbers; leading + or - allowed.
// isPositiveInteger (s [,eok])        True if string s is an integer > 0.
// isNonnegativeInteger (s [,eok])     True if string s is an integer >= 0.
// isNegativeInteger (s [,eok])        True if s is an integer < 0.
// isNonpositiveInteger (s [,eok])     True if s is an integer <= 0.
// isFloat (s [,eok])                  True if string s is an unsigned floating point (real) number. (Integers also OK.)
// isSignedFloat (s [,eok])            True if string s is a floating point number; leading + or - allowed. (Integers also OK.)
// isAlphabetic (s [,eok])             True if string s is English letters 
// isAlphanumeric (s [,eok])           True if string s is English letters and numbers only.
// 
// isUSPhoneNumber (s [,eok])          True if string s is a valid U.S. Phone Number. 
// isZIPCode (s [,eok])                True if string s is a valid U.S. ZIP code.
// isEmail (s [,eok])                  True if string s is a valid email address.


// FUNCTIONS TO REFORMAT DATA:
//
// stripCharsInBag (s, bag)            Removes all characters in string bag from string s.
// stripCharsNotInBag (s, bag)         Removes all characters NOT in string bag from string s.
// stripWhitespace (s)                 Removes all whitespace characters from s.
// stripInitialWhitespace (s)          Removes initial (leading) whitespace characters from s.
// reformat (TARGETSTRING, STRING,     Function for inserting formatting characters or
//   INTEGER, STRING, INTEGER ... )       delimiters into TARGETSTRING.                                       
// reformatZIPCode (ZIPString)         If 9 digits, inserts separator hyphen.
// reformatUSPhone (USPhone)           Reformats as (123) 456-789.


// FUNCTIONS TO PROMPT USER:
//
// prompt (s)                          Display prompt string s in status bar.
// promptEntry (s)                     Display data entry prompt string s in status bar.
// warnEmpty (theField, s)             Notify user that required field theField is empty.
// warnInvalid (theField, s)           Notify user that contents of field theField are invalid.


// FUNCTIONS TO INTERACTIVELY CHECK FIELD CONTENTS:
//
// checkString (theField, s [,eok])    Check that theField.value is not empty or all whitespace.
// checkZIPCode (theField [,eok])      Check that theField.value is a valid ZIP code.
// checkUSPhone (theField [,eok])      Check that theField.value is a valid US Phone.
// checkEmail (theField [,eok])        Check that theField.value is a valid Email.


// 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.
//
// 22 March 2001 Tom James
//
// (c) 2001 divine, Inc.



// 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;

// 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

// 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 sZIPCode = "ZIP Code"
var sPhone = "Phone Number"
var sEmail = "Email"


// i is an abbreviation for "invalid"

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 iEmail = "This field must be a valid email address (like foo@bar.com). Please reenter it now."

// p is an abbreviation for "prompt"

var pEntryPrompt = "Please enter a "
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 pEmail = "valid email address (like foo@bar.com)."

// 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


// 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 makeArray(n) {
//*** BUG: If I put this line in, I get two error messages:
//(1) Window.length can't be set by assignment
//(2) 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
}

// 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 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;
}

// Removes all characters which appear in string bag from string s.

function 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 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 stripWhitespace (s)

{   return 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 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 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 isLetter (c)
{   return ( ((c >= "a") && (c <= "z")) || ((c >= "A") && (c <= "Z")) )
}

// Returns true if character c is a digit 
// (0 .. 9).

function isDigit (c)
{   return ((c >= "0") && (c <= "9"))
}

// Returns true if character c is a letter or digit.

function isLetterOrDigit (c)
{   return (isLetter(c) || isDigit(c))
}

// 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:
// isInteger ("5")            true 
// isInteger ("")             defaultEmptyOK
// isInteger ("-5")           false
// isInteger ("", true)       true
// isInteger ("", false)      false
// isInteger ("5", false)     true

function isInteger (s)

{   var i;

    if (isEmpty(s)) 
       if (isInteger.arguments.length == 1) return defaultEmptyOK;
       else return (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 (!isDigit(c)) return false;
    }

    // All characters are numbers.
    return true;
}

// 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 isInteger.
//
// EXAMPLE FUNCTION CALL:          RESULT:
// isSignedInteger ("5")           true 
// isSignedInteger ("")            defaultEmptyOK
// isSignedInteger ("-5")          true
// isSignedInteger ("+5")          true
// isSignedInteger ("", false)     false
// isSignedInteger ("", true)      true

function isSignedInteger (s)

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

    else {
        var startPos = 0;
        var secondArg = defaultEmptyOK;

        if (isSignedInteger.arguments.length > 1)
            secondArg = isSignedInteger.arguments[1];

        // skip leading + or -
        if ( (s.charAt(0) == "-") || (s.charAt(0) == "+") )
           startPos = 1;    
        return (isInteger(s.substring(startPos, s.length), secondArg))
    }
}

// isPositiveInteger (STRING s [, BOOLEAN emptyOK])
// 
// Returns true if string s is an integer > 0.
//
// For explanation of optional argument emptyOK,
// see comments of function isInteger.

function isPositiveInteger (s)
{   var secondArg = defaultEmptyOK;

    if (isPositiveInteger.arguments.length > 1)
        secondArg = 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 (isSignedInteger(s, secondArg)
         && ( (isEmpty(s) && secondArg)  || (parseInt (s) > 0) ) );
}

// isNonnegativeInteger (STRING s [, BOOLEAN emptyOK])
// 
// Returns true if string s is an integer >= 0.
//
// For explanation of optional argument emptyOK,
// see comments of function isInteger.

function isNonnegativeInteger (s)
{   var secondArg = defaultEmptyOK;

    if (isNonnegativeInteger.arguments.length > 1)
        secondArg = 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 (isSignedInteger(s, secondArg)
         && ( (isEmpty(s) && secondArg)  || (parseInt (s) >= 0) ) );
}

// isNegativeInteger (STRING s [, BOOLEAN emptyOK])
// 
// Returns true if string s is an integer < 0.
//
// For explanation of optional argument emptyOK,
// see comments of function isInteger.

function isNegativeInteger (s)
{   var secondArg = defaultEmptyOK;

    if (isNegativeInteger.arguments.length > 1)
        secondArg = 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 (isSignedInteger(s, secondArg)
         && ( (isEmpty(s) && secondArg)  || (parseInt (s) < 0) ) );
}

// isNonpositiveInteger (STRING s [, BOOLEAN emptyOK])
// 
// Returns true if string s is an integer <= 0.
//
// For explanation of optional argument emptyOK,
// see comments of function isInteger.

function isNonpositiveInteger (s)
{   var secondArg = defaultEmptyOK;

    if (isNonpositiveInteger.arguments.length > 1)
        secondArg = 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 (isSignedInteger(s, secondArg)
         && ( (isEmpty(s) && secondArg)  || (parseInt (s) <= 0) ) );
}

// 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 isInteger, then call isFloat.
//
// Does not accept exponential notation.
//
// For explanation of optional argument emptyOK,
// see comments of function isInteger.

function isFloat (s)

{   var i;
    var seenDecimalPoint = false;

    if (isEmpty(s)) 
       if (isFloat.arguments.length == 1) return defaultEmptyOK;
       else return (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 (!isDigit(c)) return false;
    }

    // All characters are numbers.
    return true;
}

// 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 isSignedInteger, then call isSignedFloat.
//
// Does not accept exponential notation.
//
// For explanation of optional argument emptyOK,
// see comments of function isInteger.

function isSignedFloat (s)

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

    else {
        var startPos = 0;
        var secondArg = defaultEmptyOK;

        if (isSignedFloat.arguments.length > 1)
            secondArg = isSignedFloat.arguments[1];

        // skip leading + or -
        if ( (s.charAt(0) == "-") || (s.charAt(0) == "+") )
           startPos = 1;    
        return (isFloat(s.substring(startPos, s.length), secondArg))
    }
}

// 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;
}

// 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 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 isAlphanumeric (s)

{   var i;

    if (isEmpty(s)) 
       if (isAlphanumeric.arguments.length == 1) return defaultEmptyOK;
       else return (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 (! (isLetter(c) || isDigit(c) ) )
        return false;
    }

    // All characters are numbers or letters.
    return true;
}

// reformat (TARGETSTRING, STRING, INTEGER, STRING, INTEGER ... )       
//
// Handy function for arbitrarily inserting formatting characters
// or delimiters of various kinds within TARGETSTRING.
//
// 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.
//
// reformat processes the other arguments in order one by one.
// * If the argument is an integer, reformat appends that number 
//   of sequential characters from s to the resultString.
// * If the argument is a string, 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 reformat a 10-digit U.S. phone number from "1234567890"
//   to "(123) 456-7890" make this function call:
//   reformat("1234567890", "(", 3, ") ", 3, "-", 4)
//
// * To reformat a 9-digit U.S. Social Security number from
//   "123456789" to "123-45-6789" make this function call:
//   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 reformat,
// call function stripCharsNotInBag to remove the unwanted 
// characters, THEN call function reformat to delimit as desired.
//
// EXAMPLE:
//
// reformat (stripCharsNotInBag ("123 456 7890", digits),
//           "(", 3, ") ", 3, "-", 4)

function reformat (s)

{   var arg;
    var sPos = 0;
    var resultString = "";

    for (var i = 1; i < reformat.arguments.length; i++) {
       arg = reformat.arguments[i];
       if (i % 2 == 1) resultString += arg;
       else {
           resultString += s.substring(sPos, sPos + arg);
           sPos += arg;
       }
    }
    return resultString;
}

// isUSPhoneNumber (STRING s [, BOOLEAN emptyOK])
// 
// 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 isInteger.

function isUSPhoneNumber (s)
{   if (isEmpty(s)) 
       if (isUSPhoneNumber.arguments.length == 1) return defaultEmptyOK;
       else return (isUSPhoneNumber.arguments[1] == true);
    return (isInteger(s) && s.length == digitsInUSPhoneNumber)
}


// isZIPCode (STRING s [, BOOLEAN emptyOK])
// 
// 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 isInteger.

function isZIPCode (s)
{  if (isEmpty(s)) 
       if (isZIPCode.arguments.length == 1) return defaultEmptyOK;
       else return (isZIPCode.arguments[1] == true);
   return (isInteger(s) && 
            ((s.length == digitsInZIPCode1) ||
             (s.length == digitsInZIPCode2)))
}

// 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;
}


/* FUNCTIONS TO NOTIFY USER OF INPUT REQUIREMENTS OR MISTAKES. */


// Display prompt string s in status bar.

function prompt (s)
{   window.status = s
}

// Display data entry prompt string s in status bar.

function 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 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 warnInvalid (theField, s)
{   theField.focus()
    theField.select()
    alert(s)
    return false
}

/* FUNCTIONS TO INTERACTIVELY CHECK VARIOUS FIELDS. */

// 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 isInteger.

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

// takes ZIPString, a string of 5 or 9 digits;
// if 9 digits, inserts separator hyphen

function reformatZIPCode (ZIPString)
{   if (ZIPString.length == 5) return ZIPString;
    else return (reformat (ZIPString, "", 5, "-", 4));
}

// 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 isInteger.

function checkZIPCode (theField, emptyOK)
{   if (checkZIPCode.arguments.length == 1) emptyOK = defaultEmptyOK;
    if ((emptyOK == true) && (isEmpty(theField.value))) return true;
    else
    { var normalizedZIP = stripCharsInBag(theField.value, ZIPCodeDelimiters)
      if (!isZIPCode(normalizedZIP, false)) 
         return warnInvalid (theField, iZIPCode);
      else 
      {  // if you don't want to insert a hyphen, comment next line out
         theField.value = reformatZIPCode(normalizedZIP)
         return true;
      }
    }
}


// takes USPhone, a string of 10 digits
// and reformats as (123) 456-789

function reformatUSPhone (USPhone)
{   return (reformat (USPhone, "(", 3, ") ", 3, "-", 4))
}

// 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 isInteger.

function checkUSPhone (theField, emptyOK)
{   if (checkUSPhone.arguments.length == 1) emptyOK = defaultEmptyOK;
    if ((emptyOK == true) && (isEmpty(theField.value))) return true;
    else
    {  var normalizedPhone = stripCharsInBag(theField.value, phoneNumberDelimiters)
       if (!isUSPhoneNumber(normalizedPhone, false)) 
          return warnInvalid (theField, iUSPhone);
       else 
       {  // if you don't want to reformat as (123) 456-789, comment next line out
          theField.value = reformatUSPhone(normalizedPhone)
          return true;
       }
    }
}

// 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 isInteger.

function checkEmail (theField, emptyOK)
{   if (checkEmail.arguments.length == 1) emptyOK = defaultEmptyOK;
    if ((emptyOK == true) && (isEmpty(theField.value))) return true;
    else if (!isEmail(theField.value, false)) 
       return warnInvalid (theField, iEmail);
    else return true;
}