function GEBI(id) {
  return document.getElementById(id);
}

var labels = new Array();
function getLabelForField(id) {
    
  if(labels.length == 0) {
    labels = document.getElementsByTagName("label");
  }
  for(var i=0;i<labels.length;i++) {
    if(labels[i].htmlFor == id) 
	  return labels[i];
  }
  return false;
}

/**
 * Check if an email address has the valid format
 * @param email
 * @return
 */
function isEmail(email) {
  return email.match(/^[_A-Za-z0-9-]+(\.[_A-Za-z0-9-]+)*@[A-Za-z0-9-]+(\.[A-Za-z0-9-]+)*(\.[_A-Za-z0-9-]+)$/);
}

var Errorfields = new Array();
function AddErrorfield(id) {
  Errorfields[Errorfields.length] = id;
}

function MarkErrors() {
  var lbl;
  for(var i=0;i<Errorfields.length;i++) {
    lbl = getLabelForField(Errorfields[i]);
	if(lbl) {
	  lbl.style.color = "red";
	}
  }
}

function unMarkErrors() {
  var lbl;
  
  for(var i=0;i<Errorfields.length;i++) {
    lbl = getLabelForField(Errorfields[i]);
	if(lbl) {
	  lbl.style.color = "black";
	}
  }
  Errorfields = new Array();
  labels = new Array();
}

function mailformCheck() {
  unMarkErrors();
  
  if(GEBI("email").value == "")
    AddErrorfield("email");
	
  else {
    if(!isEmail(GEBI("email").value))
	  AddErrorfield("email");
  }
  if(GEBI("naam").value == "")
    AddErrorfield("naam");
  MarkErrors();
  
  return (Errorfields.length == 0);
}