Core options

Select2 supports a small subset of options in every build that is generated. Each option typically has a decorator that is required that wraps an adapter, adding support for the option. This is only required when a custom adapter is being used, as Select2 will build the required adapters by default.

Select2 will automatically apply decorators to any adapters which have not been manually overridden. The only time you need to decorate adapters is when you are using third-party adapters not provided by Select2, or you are using features not provided in the Select2 core. You can apply a decorator to an adapter using the Utils.Decorate method provided with Select2.

$.fn.select2.amd.require(
    ["select2/utils", "select2/selection/single", "select2/selection/placeholder"],
    function (Utils, SingleSelection, Placeholder) {
  var CustomSelectionAdapter = Utils.Decorate(SingleSelection, Placeholder);
});

All core options that use decorators or adapters will clearly state it in the "Decorator" or "Adapter" part of the documentation. Decorators are typically only compatible with a specific type of adapter, so make sure to note what adapter is given.

Declaring configuration in the data-* attributes

It is recommended that you declare your configuration options for Select2 when initializing Select2. You can also define your configuration options by using the HTML5 data-* attributes, which will override any options set when initializing Select2 and any defaults.

This means that if you declare your <select> tag as...

<select data-tags="true" data-placeholder="Select an option"></select>

Will be interpreted the same as initializing Select2 as...

$("select").select2({
  tags: "true",
  placeholder: "Select an option"
});

You can also define nested configurations, which are typically needed for options such as AJAX. Each level of nesting should be separated by two dashes (--) instead of one. Due to a jQuery bug, nested options using data-* attributes do not work in jQuery 1.x.

<select data-ajax--url="http://example.org/api/test" data-ajax--cache="true"></select>

Which will be interpreted the same as initializing Select2 with...

$("select").select2({
  ajax: {
    url: "http://example.org/api/test",
    cache: "true"
  }
});

The value of the option is subject to jQuery's parsing rules for HTML5 data attributes.

AMD compatibility

You can find more information on how to integrate Select2 with your existing AMD-based project by viewing the 4.0 release notes. Select2 automatically loads some modules when the adapters are being automatically constructed, so those who are using Select2 with a custom AMD build using their own system may need to specify the paths that are generated to the Select2 modules.

Key
amdBase
Default
select2/
Key
amdLanguageBase
Default
select2/i18n/

Displaying selections

Select2 provides options that allow you to directly affect how the container that holds the current selection is displayed.

Placeholders

Select2 can display a placeholder for a single-value select that will replace an option, or be shown when no options are selected for multiple-value selects. You can find an example on the example page.

Key
placeholder
Value
string or object

Adapter
SelectionAdapter
Decorator
Placeholder and HidePlaceholder
Heads up! Because browsers assume that the first option in single-value select boxes is selected, you should add an empty <option></option> tag that the placeholder should use or it may not work.

If the value is a string, the placeholder will be displayed when a blank option is used as the placeholder. The value will be the message to show to users as the placeholders.

placeholder: "Select a repository"

If the value is an object, the object should be compatible with Select2's internal objects. The id should be the id to look for when determining if the placeholder should be displayed. The text should be the placeholder to display when that option is selected.

placeholder: {
  id: "-1",
  text: "Select a repository"
}
You should pass in an object when you are using a framework that creates its own placeholder option. The id should be the same as the value attribute on the option.

You can allow a selected option to be cleared back to the placeholder by enabling the allowClear option.

Key
allowClear
Value
boolean
Adapter
SelectionAdapter
Decorator
AllowClear

This will display an "x" that the user can click to clear the current selection. It is designed to be used for cases where a single selection can be made.

Multiple selections

Select2 can display either a single selection or multiple selections.

Key
multiple
Value
boolean (true or false)

This option will determine what the SelectAdapter (used by default) should use to set the value of the underlying select element. It will also determine if the MultipleSelection adapter should be used.

Container width

Select2 will try to match the width of the original element as closely as possible. Sometimes this isn't perfect, which is what you can tell Select2 how to determine the width.

Value Description
"element" Uses javascript to calculate the width of the source element.
"style" Copies the value of the width style attribute set on the source element.
"resolve" Tries to use style to determine the width, falling back to element.
Anything else The value of the width option is directly set as the width of the container.
Key
width
Value
string

Internationalization (Language support)

Messages will be displayed to users when necessary, such as when no search results were found or more characters need to be entered in order for a search to be made. These messages have been translated into many languages by contributors to Select2, but you can also provide your own translations.

Key
language
Value
object or string

Module
Translation

Heads up! When using translations provided by Select2, you must make sure to include the translation file in your page after Select2.

When a string is passed in as the language, Select2 will try to resolve it into a language file. This allows you to specify your own language files, which must be defined as an AMD module. If the language file cannot be found, Select2 will assume it is a language code controlled by Select2, and it will try to load the translations for that language instead.

You can include your own translations by providing an object similar to the one below.

language: {
  // You can find all of the options in the language files provided in the
  // build. They all must be functions that return the string that should be
  // displayed.
  inputTooShort: function () {
    return "You must enter more characters...";
  }
}

Templating results and selections

By default, Select2 will display the option text within the list of results and when the option has been selected. Select2 comes with options that allow you to further customize the display of results and selections, allowing you to display them however you want.

Customizing the display of selections

When an option is displayed after it has been selected, it is passed through a formatting function that determines what is displayed. By default, the function only returns the text key of the data object.

Key
templateSelection
Value
A function taking a selection object
Anything rendered as a selection is templated. This includes placeholders and pre-existing selections that are displayed, so you must ensure that your templating functions can support them.

The templateSelection function should return a string containing the text to be displayed, or an object (such as a jQuery object) that contains the data that should be displayed.

Strings are assumed to contain only text and will be passed through the escapeMarkup function, which strips any HTML markup.

Anything else will be passed directly to jQuery.fn.append and will be handled directly by jQuery. Any markup, such as HTML, returned will not be escaped and it is up to you to escape any malicious input provided by users.

Customizing the display of results

When an option is displayed after it has been selected, it is passed through a formatting function that determines what is displayed. By default, the function only returns the text key of the data object.

Key
templateResult
Value
A function taking a result object
Anything rendered in the results is templated. This includes results such as the "Searching..." and "Loading more..." text which will periodically be displayed, which allows you to add more advanced formatting to these automatically generated options.

The templateResult function should return a string containing the text to be displayed, or an object (such as a jQuery object) that contains the data that should be displayed. It can also return null, which will prevent the option from being displayed in the results list.

Strings are assumed to contain only text and will be passed through the escapeMarkup function, which strips any HTML markup.

Anything else will be passed directly to jQuery.fn.append and will be handled directly by jQuery. Any markup, such as HTML, returned will not be escaped and it is up to you to escape any malicious input provided by users.

Returning and displaying results

Select2 can work on many different data sets ranging from local options, the same way that a <select> typically works, from remote options where a server generates the results that users can select from.

Array

Select2 allows creating the results based on an array of data objects that is included when initializing Select2.

Key
data
Value
array of objects
Adapter
ArrayAdapter

The objects that the users can select from should be passed as an array with each object containing id and text properties.

AJAX

Select2 allows searching for results from remote data sources using AJAX requests.

Key
ajax
Value
object
Adapter
AjaxAdapter

All options passed to this option will be directly passed to the $.ajax function that executes AJAX requests. There are a few custom options that Select2 will intercept, allowing you to customize the request as it is being made.

ajax: {
  // The number of milliseconds to wait for the user to stop typing before
  // issuing the ajax request.
  delay: 250,
  // You can craft a custom url based on the parameters that are passed into the
  // request. This is useful if you are using a framework which has
  // JavaScript-based functions for generating the urls to make requests to.
  //
  // @param params The object containing the parameters used to generate the
  //   request.
  // @returns The url that the request should be made to.
  url: function (params) {
    return UrlGenerator.Random();
  },
  // You can pass custom data into the request based on the parameters used to
  // make the request. For `GET` requests, the default method, these are the
  // query parameters that are appended to the url. For `POST` requests, this
  // is the form data that will be passed into the request. For other requests,
  // the data returned from here should be customized based on what jQuery and
  // your server are expecting.
  //
  // @param params The object containing the parameters used to generate the
  //   request.
  // @returns Data to be directly passed into the request.
  data: function (params) {
    var queryParameters = {
      q: params.term
    }

    return queryParameters;
  },
  // You can modify the results that are returned from the server, allowing you
  // to make last-minute changes to the data, or find the correct part of the
  // response to pass to Select2. Keep in mind that results should be passed as
  // an array of objects.
  //
  // @param data The data as it is returned directly by jQuery.
  // @returns An object containing the results data as well as any required
  //   metadata that is used by plugins. The object should contain an array of
  //   data objects as the `results` key.
  processResults: function (data) {
    return {
      results: data
    };
  },
  // You can use a custom AJAX transport function if you do not want to use the
  // default one provided by jQuery.
  //
  // @param params The object containing the parameters used to generate the
  //   request.
  // @param success A callback function that takes `data`, the results from the
  //   request.
  // @param failure A callback function that indicates that the request could
  //   not be completed.
  // @returns An object that has an `abort` function that can be called to abort
  //   the request if needed.
  transport: function (params, success, failure) {
    var $request = $.ajax(params);

    $request.then(success);
    $request.fail(failure);

    return $request;
  }
}

Tags

Users can create their own options based on the text that they have entered.

Key
tags
Value
boolean / array of objects
Adapter
DataAdapter
Decorator
Tags

If the tags option is passed into Select2, if a user types anything into the search box which doesn't already exist, it will be displayed at the top and the user will be able to select it.

For backwards compatibility, if an array of objects is passed in with the tags option, the options will be automatically created and the user will be able to select from them. This is the same as how array data works, and has similar limitations.

Change how options are matched when searching

When users filter down the results by entering search terms into the search box, Select2 uses an internal "matcher" to match search terms to results. When a remote data set is used, Select2 expects that the returned results have already been filtered.

Key
matcher
Value
A function taking search params and the data object.

Select2 will pass the individual data objects that have been passed back from the data adapter into the matcher individually to determine if they should be displayed. Only the first-level objects will be passed in, so if you are working with nested data, you need to match those individually.

matcher: function (params, data) {
  // If there are no search terms, return all of the data
  if ($.trim(params.term) === '') {
    return data;
  }

  // `params.term` should be the term that is used for searching
  // `data.text` is the text that is displayed for the data object
  if (data.text.indexOf(params.term) > -1) {
    var modifiedData = $.extend({}, data, true);
    modifiedData.text += ' (matched)';

    // You can return modified objects from here
    // This includes matching the `children` how you want in nested data sets
    return modifiedData;
  }

  // Return `null` if the term should not be displayed
  return null;
}

This allows for more advanced matching when working with nested objects, allowing you to handle them however you want. For those who are not looking to implement highly customized matching, but instead are just looking to change the matching algorithm for the text, a compatibility modules has been created to make it easier.

Select2 allows you to change the way that the dropdown works, allowing you to do anything from attach it to a different location in the document or add a search box.

By default, Select2 will attach the dropdown to the end of the body and will absolutely position it to appear below the selection container.

Key
dropdownParent
Value
jQuery element or DOM node

Adapter
DropdownAdapter
Decorator
AttachBody
Heads up! This will cause DOM events to be raised outside of the standard Select2 DOM container. This can cause issues with third-party components such as modals.

When the dropdown is attached to the body, you are not limited to just displaying the dropdown below the container. Select2 will display above the container if there is not enough space below the container, but there is enough space above it. You are also not limited to displaying the dropdown within the parent container, which means Select2 will render correctly inside of modals and other small containers.

Select2 can place the dropdown directly after the selection container, so it will appear in the same location within the DOM as the rest of Select2.

Adapter
DropdownAdapter
Decorator
AttachContainer
Check your build. This module is only included in the full builds of Select2.
Harvest Chosen migrators! If you are migrating to Select2 from Chosen, this option will cause Select2 to position the dropdown in a similar way.

Users can filter down the results by typing a search term into a box that is displayed at the top of the dropdown.

Adapter
DropdownAdapter
Decorator
DropdownSearch

A search box is added to the top of the dropdown automatically for select boxes where only a single option can be selected.

Sometimes when working with large data sets, it is more efficient to start filtering the results when the search term is a certain length. This is very common when working with remote data sets, as allows for only significant search terms to be used.

Key
minimumInputLength
Value
integer
Adapter
DataAdapter
Decorator
MinimumInputLength

In some cases, search terms need to be limited to a certain range. Select2 allows you to limit the length of the search term such that it does not exceed a certain length.

Key
maximumInputLength
Value
integer
Adapter
DataAdapter
Decorator
MaximumInputLength

When working with smaller data sets, the search box can take up more space that is necessary, as there are not enough results for filtering to be effective. Select2 allows you to only display the search box when the number of search results reaches a certain threshold.

Key
minimumResultsForSearch
Value
integer
Adapter
DropdownAdapter
Decorator
MinimumResultsForSearch

When users close the dropdown, the last highlighted option can be automatically selected. This is commonly used in combination with tagging and placeholders and other situations where the user is required to select an option, or they need to be able to quickly select multiple options.

Adapter
ResultsAdapter
Decorator
SelectOnClose

Close the dropdown when a result is selected

Select2 will automatically close the dropdown when an element is selected, similar to what is done with a normal select box. This behavior can be changed though to keep the dropdown open when results are selected, allowing for multiple options to be selected quickly.

Key
closeOnSelect
Default
true
Adapter
DropdownAdapter
Decorator
CloseOnSelect

If this decorator is not used (or closeOnSelect is set to false), the dropdown will not automatically close when a result is selected. The dropdown will also never close if the ctrl key is held down when the result is selected.

Select2 has an internal event system that is used to notify parts of the component that state has changed, as well as an adapter that allows some of these events to be relayed to the outside word.

Adapter
SelectionAdapter
Decorator
EventRelay

Public events

All public events are relayed using the jQuery event system, and they are triggered on the <select> element that Select2 is attached to. You can attach to them using the .on method provided by jQuery.

Internal events

Select2 triggers internal events using its own internal event system, which allows adapters to communicate with each other. These events are not accessible through the jQuery event system.

You can find more information on the public events triggered by individual adapters in the individual adapter documentation.

Select2 allows plugins to add additional functionality through the core adapters. You can change almost anything involving the way Select2 works to the way Select2 interacts with the page by modifying the core adapters. Most third-party plugins should provide decorators (used to wrap adapters) and custom adapters that you can use.

Each adapter contains a set of methods which will must always be defined. Along with the global methods that all adapters must implement, these methods must be implemented.

All adapters

All adapters must implement a set of methods that Select2 will use to display them and bind any internal events.

// The basic HTML that should be rendered by Select2. A jQuery or DOM element
// should be returned, which will automatically be placed by Select2 within the
// DOM.
//
// @returns A jQuery or DOM element that contains any elements that must be
//   rendered by Select2.
Adapter.render = function () {
  return $jq;
};

// Bind to any Select2 or DOM events.
//
// @param container The Select2 object that is bound to the jQuery element.  You
//   can listen to Select2 events with `on` and trigger Select2 events using the
//   `trigger` method.
// @param $container The jQuery DOM node that all default adapters will be
//   rendered within.
Adapter.bind = function (container, $container) { };

// Position the DOM element within the Select2 DOM container, or in another
// place. This allows adapters to be located outside of the Select2 DOM,
// such as at the end of the document or in a specific place within the Select2
// DOM node.
//
// Note: This method is not called on data adapters.
//
// @param $rendered The rendered DOM element that was returned from the call to
//   `render`. This may have been modified by Select2, but the root element
//   will always be the same.
// @param $defaultContainer The default container that Select2 will typically
//   place the rendered DOM element within. For most adapters, this is the
//   Select2 DOM element.
Adapter.position = function ($rendered, $defaultContainer) { };

// Destroy any events or DOM elements that have been created.
// This is called when `select2("destroy")` is called on an element.
Adapter.destroy = function () { };

Container (selection)

The selection is what is shown to the user as a replacement of the standard <select> box. It controls the display of the selection option(s), as well anything else that needs to be embedded within the container, such as a search box.

Key
selectionAdapter
Default
SingleSelection or MultipleSelection
Base
BaseSelection
// Update the selected data.
//
// @param data An array of data objects that have been generated by the data
//   adapter. If no objects should be selected, an empty array will be passed.
//
// Note: An array will always be passed into this method, even if Select2 is
// attached to a source which only accepts a single selection.
SelectionAdapter.update = function (data) { };

Data set

The data set is what Select2 uses to generate the possible results that can be selected, as well as the currently selected results.

Key
dataAdapter
Default
SelectAdapter
Base
BaseAdapter
// Get the currently selected options. This is called when trying to get the
// initial selection for Select2, as well as when Select2 needs to determine
// what options within the results are selected.
//
// @param callback A function that should be called when the current selection
//   has been retrieved. The first parameter to the function should be an array
//   of data objects.
DataAdapter.current = function (callback) {
  callback(currentData);
}

// Get a set of options that are filtered based on the parameters that have
// been passed on in.
//
// @param params An object containing any number of parameters that the query
//   could be affected by. Only the core parameters will be documented.
// @param params.term A user-supplied term. This is typically the value of the
//   search box, if one exists, but can also be an empty string or null value.
// @param params.page The specific page that should be loaded. This is typically
//   provided when working with remote data sets, which rely on pagination to
//   determine what objects should be displayed.
// @param callback The function that should be called with the queried results.
DataAdapter.query = function (params, callback) {
  callback(queryiedData);
}

The dropdown adapter defines the main container that the dropdown should be held in. It does not define any extra methods that can be used for decorators, but it is common for decorators to attach to the render and position methods to alter how the dropdown is altered and positioned.

Key
dropdownAdapter
Default
DropdownAdapter

Results

The results adapter controls the list of results that the user can select from. While the results adapter does not define any additional methods that must be implemented, it makes extensive use of the Select2 event system for controlling the display of results and messages.

Key
resultsAdapter
Default
ResultsAdapter

Setting default options

In some cases, you need to set the default options for all instances of Select2 in your web application. This is especially useful when you are migrating from past versions of Select2, or you are using non-standard options like custom AMD builds. Select2 exposes the default options through $.fn.select2.defaults, which allows you to set them globally.

When setting options globally, any past defaults that have been set will be overriden. Default options are only used when an option is requested that has not been set during initialization.

You can set default options by calling $.fn.select2.defaults.set("key", "value"). The key that is set should take the same format as keys set using HTML data-* attributes which means that two dashes (--) will be replaced by a level of nesting, and a single dash (-) will convert it to a camelCase string.

$.fn.select2.defaults.set("theme", "classic");

You can reset the default options by calling $.fn.select2.defaults.reset().

Select2 offers limited backwards compatibility with the previously 3.5.x release line, allowing people more efficiently transfer across releases and get the latest features. For many of the larger changes, such as the change in how custom data adapters work, compatibility modules were created that will be used to assist in the upgrade process. It is not recommended to rely on these compatibility modules, as they will not always exist, but they make upgrading easier for major changes.

The compatibility modules are only included in the full builds of Select2. These files end in .full.js, and the compatibility modules are prefixed with select2/compat.

Simplified function for matching data objects

Added in Select2 4.0.0. This method was added to make upgrading easier from earlier versions of Select2.

During the Select2 4.0.0 release, the matcher function was changed to allow for more complex matching of nested objects.

Key
matcher
Value
A function taking a search term and the data object text.
Adapter
oldMatcher

The custom matcher example provides a guide for how to use this in your own application. For those upgrading from older versions of Select2, you just need to wrap your old matcher with this function to maintain compatibility.

Old initial selections with initSelection

Deprecated in Select2 4.0. This has been replaced by another option and is only available in the full builds of Select2.

In the past, Select2 required an option called initSelection that was defined whenever a custom data source was being used, allowing for the initial selection for the component to be determined. This has been replaced by the current method on the data adapter.

Key
initSelection
Value
A function taking a callback
Adapter
DataAdapter
Decorator
InitSelection

Querying old data with query

Deprecated in Select2 4.0. This has been replaced by another option and is only available in the full builds of Select2.

In the past, Select2 supported an option called query that allowed for a custom data source to be used. This option has been replaced by the query method on the data adapter and takes a very similar set of parameters.

Key
query
Value
A function taking params (including a callback)
Adapter
DataAdapter
Decorator
Query

Compatibility with <input type="text" />

Deprecated in Select2 4.0. It is now encouraged to use the <select> tag instead.

In past versions of Select2, a <select> element could only be used with a limited subset of options. An <input type="hidden" /> was required instead, which did not allow for a graceful fallback for users who did not have JavaScript enabled. Select2 now supports the <select> element for all options, so it is no longer required to use <input /> elements with Select2.

Adapter
DataAdapter
Decorator
InputData