//----------------------------------------------------------------------------
// validate if requested fields are entered
//----------------------------------------------------------------------------

function FormFieldError( form, field) { 
  var obj = form.elements[ field];
	if (obj) {
		switch( obj.type) {
			case "select-one":
				if (obj.selectedIndex == -1 || obj.options[obj.selectedIndex].text == "")
          return true;
				break;
			case "select-multiple":
				if (obj.selectedIndex == -1)
          return true;
				break;
			case "text":
			case "textarea":
			default:
				if (obj.value == "" || obj.value == null)
          return true;
				break;
    }
  }
  return false;
}

function FormValidate( form, defs) { 
  var TXT_OR = " of ";
  var TXT_START = "Om uw aanvraag te kunnen verwerken, moet u (ook) de volgende gegevens invullen:\n";
  var MsgText = "";
  items = defs.split( "&");
	for (var i = 0; i < items.length; i++) {
    fields = items[ i].split( "|");
    OrText = "";
  	for (var f = 0; f < fields.length; f++) {
      field = fields[ f].split( "=");
      if (field.length == 1)
        field[ 1] = field[ 0];
      if (FormFieldError( form, field[ 0]))
        OrText += ((OrText != "")? TXT_OR : "") + field[ 1];
      else {
        OrText = "";
        break;
      }
    }
    if (OrText != "")
      MsgText += "- " + OrText + "\n";
  }
  if (MsgText != "") {
    alert( TXT_START + MsgText);
    return false;
  } else {
		return true;
  }
}