changing options_for_select from one selector

js_for_changing_options

%table
  %tr
    %td
      = f.label  :share_type, 'Share Type', class: 'required'

    %td
      = f.select :share_type, @share_types, {}, class: 'share-type', id: 'selected_share_type'
  %tr
    %td
      = f.label  :share_expiration_date, 'Expiration Date', class: 'required'

    %td#share_exp_dates
      = f.select :share_expiration_date, @share_across_dates

 
:javascript
  var share_across_options = #{@share_across_dates};
  var share_down_options = #{@share_down_dates};

  var optionsFromArray = function(array){
    var options = '';
    $(array).each(function(index, item){
      options += '<option value="' + item[1] + '">' + item[0] + '</option>'
    });
    return options;
  };

  var populateSubOptions = function(selectedOption) {
    if (selectedOption == 'share_across') {
      $('#share_exp_dates select').empty().append(optionsFromArray(share_across_options));
    } else {
      $('#share_exp_dates select').empty().append(optionsFromArray(share_down_options));
    }
  };

  var initSubOptions = function(){
    $('#selected_share_type').change(function() {
      populateSubOptions($(this).val());
    });
  };

  $(document).ready(function(){
    initSubOptions();
  });