@atlassian/aui/src/js/aui/select2.js

import $ from './jquery';
import '../../js-vendor/jquery/plugins/jquery.select2';

/**
 * Wraps a vanilla Select2 with ADG _style_, as an auiSelect2 method on jQuery objects.
 *
 * @since 5.2
 */

/**
 * We make a copy of the original select2 so that later we might re-specify $.fn.auiSelect2 as $.fn.select2. That
 * way, calling code will be able to call $thing.select2() as if they were calling the original library,
 * and ADG styling will just magically happen.
 */
var originalSelect2 = $.fn.select2;

// AUI-specific classes
var auiContainer = 'aui-select2-container';
var auiDropdown = 'aui-select2-drop aui-dropdown2';
var auiHasAvatar = 'aui-has-avatar';

$.fn.auiSelect2 = function (first) {
    var updatedArgs;

    if ($.isPlainObject(first)) {
        var auiOpts = $.extend({}, first);
        var auiAvatarClass = auiOpts.hasAvatar ? ' ' + auiHasAvatar : '';
        //add our classes in addition to those the caller specified
        auiOpts.containerCssClass  = auiContainer + auiAvatarClass + (auiOpts.containerCssClass ? ' ' + auiOpts.containerCssClass : '');
        auiOpts.dropdownCssClass  = auiDropdown + auiAvatarClass + (auiOpts.dropdownCssClass  ? ' ' + auiOpts.dropdownCssClass : '');
        updatedArgs = Array.prototype.slice.call(arguments, 1);
        updatedArgs.unshift(auiOpts);
    } else if (!arguments.length) {
        updatedArgs = [{
            containerCssClass: auiContainer,
            dropdownCssClass: auiDropdown
        }];
    } else {
        updatedArgs = arguments;
    }

    return originalSelect2.apply(this, updatedArgs);
};