code: function toggleClass(...args) {
      const cssClass = args[0];
      const enable = (args.length === 2) ? args[1] : !this.classList.contains(cssClass);
      this.classList[enable ? 'add' : 'remove'](cssClass);
    }
docs: Toggle a CSS Class.
  
  Why do we have this? Well, sadly as long as we support IE11 which has an incorrect implementation
  of node.classList.toggle, we will have to do this ourselves.
  
  @method toggleClass
  @param {String} className
  @param {Boolean} [enable=!enable]