This is the first beta release of Select2 4.0.

You can view the 4.0 release announcement for a detailed look into the changes in Select2. This is a full rewrite of the core Select2 code.

New features

• Advanced plugin system that uses custom adapters
• AMD based build system
• Declarative configuration through data-* attributes
• Easy to configure theme system and new default theme

Breaking changes

• Select2 now uses the MIT license
• <select> has replaced <input type="hidden" /> for all options (including remote data)
• The matcher has been revamped to include full context, a compatibility module (select2/compat/matcher) has been created
• The display always reflects the order data is sent to the server
• The click mask is no longer the default (again). You can get back the old functionality by wrapping your selectionAdapter with the ClickMask (select2/selection/clickMask) decorator.

Renamed options

• formatSelection -> templateSelection
• formatResult -> templateResult
• sortResults -> sorter
• ajax.jsonpCallback -> ajax.jsonp
• ajax.results -> ajax.processResults
• tags: [array,of,data] -> data: [array,of,data], tags: true
• placeholderOption has been replaced by placeholder.id (placeholder -> placeholder.text)

Internationalization

• formatNoMatches -> language.noMatches
• formatSearching -> language.searching
• formatInputTooShort -> language.inputTooShort
• formatInputTooLong -> language.inputTooLong
• formatAjaxError -> language.errorLoading
• formatLoading -> language.loadingMore
• formatSelectionTooBig -> language.maximumSelected

Renamed methods

• .select2("val", [value]) -> .val([value])
• .select2("enable", !disabled) -> .prop("disabled", disabled)

Removed options

• initSelection - This is no longer needed with <select> tags - Read more in the announcement
• id - Data objects should now always have id and text attributes that are strings, use $.map when migrating
• query - Use a custom data adapter instead - Read more in the announcement
• ajax.params - All parameters passed to ajax will be passed to the AJAX data transport function

Removed methods

• .select2("onSortStart") and .select2("onSortEnd") - A custom selection adapter should be created instead
• .select2("data", data) - Create the <option> tags for the objects that you would like to set, and set the .val to select them
• .select2("readonly") - There is no way to make a <select> element read-only, disable it instead