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

function addResizeEvent(func) {
  var oldonresize = window.onresize;
  if (typeof window.onresize != 'function') {
    window.onresize = func;
  } else {
    window.onresize = function() {
      oldonresize();
      func();
    }
  }
}

function toggleKleur(kleurId) {
	el = document.getElementById(kleurId);
	
	if (el.style.display == 'none') {
		el.style.display = 'block';
	} else {
		el.style.display = 'none';
	}
	
}

function hideKleur(kleurId) {
	el = document.getElementById(kleurId);
	
	el.style.display = 'none';
	
}