Drupal 8 comes with client-side JavaScript form validation; however, for a submit button with #ajax, it is disabled. How can I enable it?

  • Only via custom code that would fire before mousedown event on the button. – user21641 Dec 22 '15 at 14:07

I had the same question this morning. Here's how I got it to work.

Add an invisible button and specify the #ajax on that.

$form['actions'] = array(
  '#type' => 'actions',
  'submit' =>array(
    '#type' => 'submit',
    '#value' => 'Submit',
  'validation-hack' => array(
    '#type' => 'button',
    '#value' => 'validated',
    '#attributes' => array('style' => 'display:none'),
    '#ajax' => array(
      'callback' => array($this, 'doSomething'),
      'event' => 'click',
      'progress' => array(
        'type' => 'throbber',
        'message' => 'Example...',

Then add a submit handler on the form that stops the form submission and then calls click on the hidden button.

  (function($, Drupal) {
    Drupal.behaviors.example = {
      attach: function(context, settings) {
        $(context).find('#example-form-id').submit(function(evt) {
  })(jQuery, Drupal);

Hope this helps you, or anybody else that may stumble across this.

  • I just edited my answer to reflect a gotcha I just encountered. The hidden #ajax button needs to have a value assigned to ensure that it's called in all instances. If no value is specified and there are additional action buttons, it will call the #ajax on the last button if it has it or throw an exception stating that callback is empty or not callable. – konadave Jan 29 '16 at 22:28

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