Button act as submit button in form API

Question

I have a button element in form builder as follows

$form['fieldset']['add_new_event_btn'] = array(
  '#value' => t('Add new event trigger'),
  '#type' => 'button',
  '#attributes' => array(
    'style' => 'margin-top:20px;width:200px;margin-right:275px;float:right',
  ),
  '#ajax' => array(
    // Function to call when event on form element triggered.
    'callback' => '::enable_event_trigger',
    // Effect when replacing content. Options: 'none' (default), 'slide', 'fade'.
    'effect' => 'fade',
    // Javascript event to trigger Ajax. Currently for: 'onchange'.
    'event' => 'click',
    'progress' => array(
      // Graphic shown to indicate ajax. Options: 'throbber' (default), 'bar'.
      'type' => 'throbber',
      // Message to show along progress graphic. Default: 'Please wait...'.
      'message' => 'loading',
    ),
  ),
);

But this button is act as the submit button , and there for the validation for other elements works and shows the error message on the next reload when i leave the page as it is, How can i rectify this problem ??

Answer 1

As mentioned in the comments, this is not supported yet but it might at some point: https://www.drupal.org/project/drupal/issues/1671190

What you can do is return false in the onclick event. For example:

$form[button] = array(
  '#type' => 'button',
  '#name' => 'button',
  '#value' => "Do some JS",
  "#attributes" => array(
    "onclick" => "doJs(); return false;",
  ),
);