code: function(node, className, force) {
          var add = (force !== undefined) ? force :
                  !(hasClass(node, className));
  
          if (add) {
              addClass(node, className);
          } else {
              removeClass(node, className);
          }
      }
docs: If the className exists on the node it is removed, if it doesn't exist it is added.
  @method toggleClass
  @for DOM
  @param {HTMLElement} element The DOM element
  @param {String} className the class name to be toggled
  @param {Boolean} addClass optional boolean to indicate whether class
  should be added or removed regardless of current state