code: function Dropdown(element, completer, option) {
      this.$el       = Dropdown.createElement(option);
      this.completer = completer;
      this.id        = completer.id + 'dropdown';
      this._data     = []; // zipped data.
      this.$inputEl  = $(element);
      this.option    = option;
  
      // Override setPosition method.
      if (option.listPosition) { this.setPosition = option.listPosition; }
      if (option.height) { this.$el.height(option.height); }
      var self = this;
      $.each(['maxCount', 'placement', 'footer', 'header', 'noResultsMessage', 'className'], function (_i, name) {
        if (option[name] != null) { self[name] = option[name]; }
      });
      this._bindEvents(element);
      dropdownViews[this.id] = this;
    }
docs: Construct Dropdown object.  element - Textarea or contenteditable element.