(function() {
  'use strict';

  window.utils = window.utils || {};

  var FAVORITES_BTN_CLASS = 'navbar__list-item--favorite';
  var FAVORITES_BTN_ACTIVE_CLASS = 'navbar__list-item--active';
  var ASIDENAV_EXPANDED_CLASS = 'main__aside--expanded';

  window.utils.aside = function(asideEl) {

    function init() {
      var favoritesBtn = document.querySelector('.' + FAVORITES_BTN_CLASS);
      favoritesBtn.addEventListener('click', function(event) {
        favoritesBtn.classList.toggle(FAVORITES_BTN_ACTIVE_CLASS);
        asideEl.classList.toggle(ASIDENAV_EXPANDED_CLASS);
        event.preventDefault();
      }, true);
    }
    init();
  };
})();