I would like to add autocomplete functionality to a textarea form element in Drupal 8. I have a fully functioning custom textfield which has autocomplete working on the same form. I have confirmed that the Textarea element has the processAutocomplete function. Therefore, I'm uncertain as to why this wouldn't work.

I realize that adding an autocomplete to a textarea is a bit unorthodox, but that's not the question. I have seen this done in Drupal 8, so I know it's possible. I just don't know if they used a form to accomplish it.

I have added the appropriate code in the routing file:

   path: '/my-module/test-autocomplete'
     _format: json
     _access: 'TRUE'

I have also added the field appropriately on the form:

$form['text_area'] = [
  '#type' => 'textarea',
  '#title' => t('Test text area'),
  '#default_value' => $authentication_configuration->get('text_area'),
  '#autocomplete_route_name' => 'my_module.autocomplete_name',

Finally, I have the appropriate logic in the referenced controller:

public function testAutocomplete(request $request) {
  // Set up the array to be returned and get the user input
  $matches = array();
  $input = $request->query->get('q');
  // If there is user input
  if ($input) {
    $words = explode(' ', $input);
    foreach ($words as $word) {
       * Logic for generating an autocomplete list of matches
  return new JsonResponse($matches);

1 Answer 1


Textareas don't support autocomplete out of the box, you have to get a bit creative to make it work.

First you'll need to override the attach method of the autocomplete behaviour; add a library with a JS file containing this:

(function ($) {
  Drupal.behaviors.autocomplete.attach = function attach(context) {
    var $autocomplete = $(context).find('input.form-autocomplete,textarea.form-autocomplete').once('autocomplete');
    if ($autocomplete.length) {
      var blacklist = $autocomplete.attr('data-autocomplete-first-character-blacklist');
      $.extend(Drupal.autocomplete.options, {
        firstCharacterBlacklist: blacklist || ''

      $autocomplete.autocomplete(Drupal.autocomplete.options).each(function () {
        $(this).data('ui-autocomplete')._renderItem = Drupal.autocomplete.options.renderItem;

      $autocomplete.on('compositionstart.autocomplete', function () {
        Drupal.autocomplete.options.isComposing = true;
      $autocomplete.on('compositionend.autocomplete', function () {
        Drupal.autocomplete.options.isComposing = false;

The function is a straight copy of the core attach method, with the textarea added to the selectors, and a few references altered.

Then you'll need to add the autocomplete process method to the form element (it's not there by default), and also reference your library:

use Drupal\Core\Render\Element\Textarea;


$form['text_area'] = [
  '#type' => 'textarea',
  '#title' => t('Test text area'),
  '#default_value' => $authentication_configuration->get('text_area'),
  '#autocomplete_route_name' => 'my_module.autocomplete_name',
  '#process' => [
    [Textarea::class, 'processAutocomplete'],
  '#attached' => [
    'library' => [

Clear the cache and you should see the results immediately.

  • It worked! For those who may want to do this, be sure to include the use statement above. If you don't, it will not render a textarea.
    – Travis
    Dec 11, 2018 at 17:26

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