Rails SimpleForm Select or Other input, with jQuery plugin

jquery.select_or_other.js

/**
 * SelectOrOther plugin
 *
 * works with our custom simple_form select_or_other input
 */
(function($) {
  var SelectOrOther = function(el, opts) {

    var settings = $.extend({}, $.fn.selectorother.defaults, opts), $el,
      $select, $other;

    function init() {
      $el = $(el);
      $select = $el.find(settings.select_sel);
      $other = $el.find(settings.other_sel);
      $select.change(on_change).trigger('change');
    }

    function on_change(e) {
      if ($select.val() == settings.other_key) {
        $other.removeAttr('disabled').show().focus();
      } else {
        $other.attr('disabled', 'disabled').hide();
      }
    }

    init();
  };

  $.fn.selectorother = function(options) {
    return this.each(function(idx, el) {
      var $el = $(this), key = 'selectorother';
      if ($el.data(key)) { return; }
      var selectorother = new SelectOrOther(this, options);
      $el.data(key, selectorother);
    });
  };
  // default settings
  $.fn.selectorother.defaults = {
    other_key: '--other--',
    select_sel: 'select',
    other_sel: '.other'
  };
})(jQuery);

select_or_other_input.rb

class SelectOrOtherInput < SimpleForm::Inputs::CollectionSelectInput

  include ActionView::Helpers::FormOptionsHelper
  include ActionView::Helpers::FormTagHelper

  def input
    label_method, value_method = detect_collection_methods    output = ""
    val = @builder.object.send(attribute_name)

    other_key = '--other--'
    other_val = 'Other'
    other_attributes = {
      :class => 'other',
      :placeholder => 'Enter a value',
      :value => '',
    }

    # manually convert our collection to an array
    # see source for options_from_collection_for_select()
    selected = val
    soo_options = collection.map do |element|
      [element.send(label_method), element.send(value_method)]
    end
    selected, disabled = extract_selected_and_disabled(selected)
    select_deselect = {}
    select_deselect[:selected] = extract_values_from_collection(collection, value_method, selected)
    select_deselect[:disabled] = extract_values_from_collection(collection, value_method, disabled)

    soo_options << [other_val, other_key]
    if val && select_deselect[:selected] && soo_options.rassoc(select_deselect[:selected].first).nil?
      # 'other' should be selected
      select_deselect[:selected] = other_key
      other_attributes[:value] = val
    else
      other_attributes[:disabled] = 'disabled'
    end

    output << @builder.select(attribute_name, soo_options, select_deselect.merge(input_options), input_html_options)
    output << @builder.text_field(attribute_name, other_attributes)

    output.html_safe
  end
end