docs: function shuffle() {
      var length = this.items.length;
  
      // shuffle
      for (var i = 0; i < this.items.length; i++) {
          var index = Math.floor(Math.random() * length);
          var temp = this.items[i];
  
          this.items[i] = this.items[index];
          this.items[index] = temp;
      }
  }