var defaultEmptyOK = false;
var whitespace = " \t\n\r";

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;

	var filter  = /^[a-zA-Z0-9_\-\+\!\#\$\%\*\/\?\|\^\{\}\`\~\&\'\=]+(\.[a-zA-Z0-9_\-\+\!\#\$\%\*\/\?\|\^\{\}\`\~\&\'\=]+)*\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
	return filter.test(s);
}

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

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;
}