// JavaScript Document
function formCheck(f)
{
	if(f.emailadres.value == "" || f.emailadres.value == "emailadres") 
	{
		alert("Het veld 'emailadres' is niet of onjuist ingevuld");
		return false;
	}
	
	if(!emailCheck(f.emailadres.value))
	{
		return false;
	}
	
function emailCheck( emailStr )
{
	/*
		The following pattern is used to check if the entered e-mail address
		fits the user@domain format.  It also is used to separate the username
		from the domain.
	*/

	var emailPat=/^(.+)@(.+)$/

	/*
		The following string represents the pattern for matching all special
		characters.  We don't want to allow special characters in the address.
		These characters include ( ) < > @ , ; : \ " . [ ]
	*/

	var specialChars="\\(\\)<>@,;:\\\\\\\"\\.\\[\\]"

	/*
		The following string represents the range of characters allowed in a
		username or domainname.  It really states which chars aren't allowed.
	*/

	var validChars="\[^\\s" + specialChars + "\]"

	/*
		The following pattern applies if the "user" is a quoted string (in
		which case, there are no rules about which characters are allowed
		and which aren't; anything goes).  E.g. "jiminy cricket"@disney.com
		is a legal e-mail address.
	*/

	var quotedUser="(\"[^\"]*\")"

	/*
		The following pattern applies for domains that are IP addresses,
		rather than symbolic names.  E.g. joe@[123.124.233.4] is a legal
		e-mail address. NOTE: The square brackets are required.
	*/

	var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/

	/*
		The following string represents an atom (basically a series of
		non-special characters.)
	*/

	var atom=validChars + '+'

	/*
		The following string represents one word in the typical username.
		For example, in john.doe@somewhere.com, john and doe are words.
		Basically, a word is either an atom or quoted string.
	*/

	var word="(" + atom + "|" + quotedUser + ")"

	// The following pattern describes the structure of the user
	var userPat=new RegExp("^" + word + "(\\." + word + ")*$")

	/*
		The following pattern describes the structure of a normal symbolic
		domain, as opposed to ipDomainPat, shown above.
	*/

	var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$")

	/*
		Finally, let's start trying to figure out if the supplied address is valid.

		Begin with the coarse pattern to simply break up user@domain into
		different pieces that are easy to analyze.
	*/

	var matchArray = emailStr.match( emailPat );
	if( matchArray == null )
	{
		/*
			Too many/few @'s or something; basically, this address doesn't
		 even fit the general mould of a valid e-mail address.
		*/
		alert("Het e-mailadres klopt niet (controleer de @ en .'s)");
		return false;
	}
	var user=matchArray[1];
	var domain=matchArray[2];

	// See if "user" is valid
	if( user.match( userPat ) == null )
	{
		// user is not valid
		alert("Het emailadres klopt niet (controleer de @ en .'s)");
		return false;
	}

	/*
		if the e-mail address is at an IP address (as opposed to a symbolic
		host name) make sure the IP address is valid.
	*/

	var IPArray = domain.match( ipDomainPat );
	if( IPArray != null )
	{
		// this is an IP address
		for (var i=1;i<=4;i++)
		{
			if( IPArray[i] > 255 )
			{
				alert("IP adres is niet geldig!");
				return false;
			}
		}
		return true;//everthing = OK
	}

	// Domain is symbolic name
	var domainArray = domain.match( domainPat );
	if( domainArray == null )
	{
		alert("De domeinnaam van je emailadres is niet geldig.");
		return false;
	}

	/*
		domain name seems valid, but now make sure that it ends in a
		three-letter word (like com, edu, gov) or a two-letter word,
		representing country (uk, nl), and that there's a hostname preceding
		the domain or country.

		Now we need to break up the domain to get a count of how many atoms
		it consists of.
	*/

	var atomPat = new RegExp( atom,"g" );
	var domArr = domain.match( atomPat );
	var len = domArr.length;
	if (domArr[domArr.length-1].length<2 || domArr[domArr.length-1].length>4)
	{
		// the address must end in a two letter or three letter word.
		alert("Uw emailadres moet eindigen op een geldig domein.");
		return false;
	}

	// Make sure there's a host name preceding the domain.
	if (len<2)
	{
		var errStr="Dit emailadres mist een domeinnaam!";
		alert(errStr);
		return false;
	}
		return true;
}
}