select2/src/js/select2/dropdown/dropdownCss.js

Select2 is a jQuery based replacement for select boxes. It supports searching, remote data sets, and infinite scrolling of results.

define([
  '../utils'
], function (Utils) {
  function DropdownCSS () { }

  DropdownCSS.prototype.render = function (decorated) {
    var $dropdown = decorated.call(this);

    var dropdownCssClass = this.options.get('dropdownCssClass') || '';

    if (dropdownCssClass.indexOf(':all:') !== -1) {
      dropdownCssClass = dropdownCssClass.replace(':all:', '');

      Utils.copyNonInternalCssClasses($dropdown[0], this.$element[0]);
    }

    dropdownCssClass.trim().split(' ').forEach(function(cssClass) {
      if(cssClass.length > 0) {
        $dropdown[0].classList.add(cssClass);
      }
    });

    return $dropdown;
  };

  return DropdownCSS;
});