function togglemenu() {
  var menu   = document.getElementById("navigation-menu");
  var button = document.getElementById("navigation-button");
  if (menu.style.display === 'none' || menu.style.display === '') {
    menu.style.display = 'block';
    button.className += " toggle-on";
  } else {
    menu.style.display = 'none'
    button.className = button.className.replace(/(?:^|\s)toggle-on(?:$|\s)/g , '');
  }
  //menu.class
  return;
}
function addListenersOnLoad() {
  document.getElementById("navigation-button").addEventListener("click", togglemenu);
}
document.addEventListener("DOMContentLoaded", addListenersOnLoad, false);