// JavaScript Document
function addLoadEvent(func) {
	var oldonload = window.onload;
	if (typeof window.onload != 'function') {
		window.onload = func;
	} else {
		window.onload = function() {
			oldonload ();
			func();
		}
	  }
}

function validateForm(whichform) {
  for (var i=0; i<whichform.elements.length; i++) {
    var element = whichform.elements[i];
    if (element.className.indexOf("required") != -1) {
      if (!isFilled(element)) {
        alert(element.name+" is missing.");
        return false;
      }
    }
    if (element.className.indexOf("email") != -1) {
      if (!isEmail(element)) {
        alert("No valid email address given, please check.");
        return false;
      }
    }
	if (element.className.indexOf("radio") != -1) {
      if (!isChecked(element)) {
        alert("Graag aanvinken of je akkoord gaat met de voorwaarden.");
        return false;
      }
    }
  }
  return true;
}

function isFilled(field) {
  if (field.value.length < 1) {
    return false;
  } else {
    return true;
  }
}

function isEmail(field) {
  if (field.value.indexOf("@") == -1 || field.value.indexOf(".") == -1) {
    return false;
  } else {
    return true;
  }
}

function isChecked(field) {
  if (field.checked == false) {
    return false;
  } else {
    return true;
  }
}

function prepareForms() {
  for (var i=0; i<document.forms.length; i++) {
    var thisform = document.forms[i];
	thisform.onsubmit = function() {
      return validateForm(this);
    }
  }
}
addLoadEvent(prepareForms);