Extra Bundle Required

Chosen is included in Hitman vendor bundle.

Standard Select

<select data-placeholder="Choose a country" class="form-control chosen-select">
  <option>Netherlands</option>
  <option>United Kingdom</option>
  <option>United States</option>
</select>

Multiple Select

<select data-placeholder="Choose a country" class="form-control chosen-select" multiple>
  <option>Netherlands</option>
  <option>United Kingdom</option>
  <option>United States</option>
</select>

<optgroup> Support

<select data-placeholder="Choose a country" class="form-control chosen-select">
  <optgroup label="Americas">
    <option>United States</option>
  </optgroup>
  <optgroup label="Europe">
    <option>Netherlands</option>
    <option>United Kingdom</option>
  </optgroup>
</select>
<select data-placeholder="Choose a country" class="form-control chosen-select" multiple>
  <optgroup label="Americas">
    <option>United States</option>
  </optgroup>
  <optgroup label="Europe">
    <option>Netherlands</option>
    <option>United Kingdom</option>
  </optgroup>
</select>
<script>
var config = {
  '.chosen-select'           : {},
  '.chosen-select-deselect'  : { allow_single_deselect: true },
  '.chosen-select-no-single' : { disable_search_threshold: 10 },
  '.chosen-select-no-results': { no_results_text: 'Oops, nothing found!' },
  '.chosen-select-rtl'       : { rtl: true },
  '.chosen-select-width'     : { width: '95%' }
}
for (var selector in config) {
  $(selector).chosen(config[selector]);
}
</script>