// 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 = "."

var mPrefix = "You did not enter a value into the "
var mSuffix = " field. This is a required field. Please enter it now."

var defaultEmptyOK = false



// 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
var digitsInZIPCode1 = 5
var digitsInZIPCode2 = 9

var sZIPCode = "ZIP Code"

var iZIPCode = "This field must be a 5 or 9 digit U.S. ZIP Code (like 94043). Please reenter it now."

var pZIPCode = "5 or 9 digit U.S. ZIP Code (like 94110)."


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

var sEmail = "Email"

var pEmail = "valid email address (like foo@bar.com)."



// Check whether string s is empty.

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



// 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
}





// 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;
}





// 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
}




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

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






// 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;
}






// 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;
}




// 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;
}






// 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;
}

// 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;
}



// 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)))
}




// 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;
      }
    }
}




function checkBillform()
{
if ((checkString(document.billform.BillFirst, "First Name")) && (checkString(document.billform.BillLast, "Last Name")) && (checkString(document.billform.CardNumber, "Credit Card Number")) && (checkString(document.billform.CardExp_Month, "Expiration Date, Month")) && (checkString(document.billform.CardExp_Year, "Expiration Date, Year")) && (checkEmail(document.billform.BillEmail)) && (checkString(document.billform.BillAddress1, "Address")) && (checkString(document.billform.BillCity, "City")) && (checkZIPCode(document.billform.BillZip)) && (checkEmail(document.billform.BillEmail)) && (checkString(document.billform.ShipFirst, "First Name")) && (checkString(document.billform.ShipLast, "Last Name")) && (checkString(document.billform.ShipAddress1, "Address")) && (checkString(document.billform.ShipCity, "City")) && (checkZIPCode(document.billform.ShipZip)) && (checkString(document.billform.ShipPhone, "Phone")) && (checkString(document.billform.shipping, "Shipping")) ) return true;
else return false;
}

// && (checkEmail(document.billform.ShipEmail))