function validate(f) 
{
	if (!checkLength(f.voornaam, 0, 'voornaam')) return false;
	if (!checkLength(f.naam, 1, 'naam')) return false;
	if (!checkLength(f.plaats, 2, 'plaats')) return false;
	if (!checkLength(f.slagzin, 0, 'slagzin')) return false;
		
	if (! isValidEmail(f.email.value, true)) {
		document.getElementById("errorfield").innerHTML = "Geef een geldig e-mail adres op!";
        return false;
    }
    
    return true;
  }
  
function checkForAlphaNumeric(formField)
{
    var a = formField.value;
    var b = a.replace (/[^a-zA-Z0-9]/g,"XX");
    if ((a.length < 1) || (a != b))
    {
        alert('Only alphanumerics characters are allowed!\n"' + formField.value + '" contains maybe spaces or punctuation marks.');
        formField.focus();
        formField.select();
        return false;
    }

    return true;
}

function checkForPositiveInteger(formField)
{
    var a = formField.value;
	
	var objRegExp  = /(^\d\d*$)/;
	
	//check for numeric characters
	if (!objRegExp.test(a))
	{
        alert('Only a positive number is allowed!');
        formField.focus();
        formField.select();
        return false;
    }

    return true;
}

function checkForPositiveDecimal(formField)
{
    var a = formField.value;
	
	var objRegExp  =  /(^\d\d*\.\d*$)|(^\d\d*$)|(^\.\d\d*$)/;

	//check for numeric characters
	if (!objRegExp.test(a))
	{
        alert('Only a positive number is allowed!');
        formField.focus();
        formField.select();
        return false;
    }

    return true;
}

function checkLength(formField, greaterThan, lbl)
{
	if (formField.value.length <= greaterThan)
	{
		document.getElementById("errorfield").innerHTML = "Het invoerveld '"+lbl+"' is niet ingevuld.";
       	return false;
	}
	return true;
}

function isValidEmail(email, required) {
    if (required==undefined) {   // if not specified, assume it's required
        required=true;
    }
    if (email==null) {
        if (required) {
            return false;
        }
        return true;
    }
    if (email.length==0) {  
        if (required) {
            return false;
        }
        return true;
    }
    if (! allValidChars(email)) {  // check to make sure all characters are valid
        return false;
    }
    if (email.indexOf("@") < 1) { //  must contain @, and it must not be the first character
        return false;
    } else if (email.lastIndexOf(".") <= email.indexOf("@")) {  // last dot must be after the @
        return false;
    } else if (email.indexOf("@") == email.length) {  // @ must not be the last character
        return false;
    } else if (email.indexOf("..") >=0) { // two periods in a row is not valid
	return false;
    } else if (email.indexOf(".") == email.length) {  // . must not be the last character
	return false;
    }
    return true;
}

function toggle_visibility(showIt) 
{
	var g = document.getElementById('grijs');
	g.style.width=document.body.clientWidth;
	
	var d = document.getElementById('gegevens');
	
	if (showIt)
	{
		g.style.visibility = 'visible';
		d.style.visibility = 'visible';
                document.erv_form.elements["kwal"][0].checked=true;
                document.erv_form.elements["serv"][0].checked=true;
                if (document.erv_form.elements["bestel"][0] != null)
                    document.erv_form.elements["bestel"][0].checked=true;
	}
	else
	{
		g.style.visibility = 'hidden';
		d.style.visibility = 'hidden';
	}
		
}

function validateErvaringForm(form_id) 
{
   if (document.forms[form_id].elements['voornaam'].value.length <= 0)
   {
        alert("De voornaam is niet ingevuld!");
        return false;
   }
   if (document.forms[form_id].elements['voornaam'].value.length == 1)
   {
        alert("De voornaam is niet correct!");
        return false;
   }
   if (document.forms[form_id].elements['achternaam'].value.length <= 0)
   {
        alert("De achternaam is niet ingevuld!");
        return false;
   }   
   if (document.forms[form_id].elements['achternaam'].value.length == 1)
   {
        alert("De achternaam is niet correct!");
        return false;
   }

   var reg = /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/;
   var address = document.forms[form_id].elements['email'].value;

   if(reg.test(address) == false) {
      alert("Het e-mail adres is ongeldig!");
      return false;
   }

   
   if (document.forms[form_id].elements['ervaring'].value.length <= 10)
   {
        alert("Er is geen ervaring ingevuld!");
        return false;
   }

   return true;
}