Working with forms in drupal 8

I am facing problem with "#markup" in form API.

In Drupal 7 we can use "#markup" form element which look like this:

<?php
$form['test'] = array(
    '#type' => 'markup',
    '#markup' => '<div><script src="http://localhost/drupal7/sites/all/libraries/test.js"></script></div>',
  );
?>
//Here is my custom test.js
(function($) {
    Drupal.behaviors.test = {
        attach: function(context, settings) {
            console.log('testttt');
            document.write('*Hello, there!*');
        }
    };
})(jQuery);

and above code will print "Hello, there!" when form will be render.

Now in Drupal 8 I am using below code but it prints nothing.

<?php
$form['test'] = array(
      '#markup' => '<div><script src="http://localhost/project8/sites/all/libraries/test.js"></script></div>',
    );
?>

So how can implement this functionality in Drupal 8, which is already working in Drupal 7 . Under script tag it can be local script or external script.. Please help...

Thanks

Solution

#markup still works in Drupal 8, but now it is filtered before output. As it is stated in Render API overview:

#markup: Specifies that the array provides HTML markup directly. Unless the markup is very simple, such as an explanation in a paragraph tag, it is normally preferable to use #theme or #type instead, so that the theme can customize the markup. Note that the value is passed through \Drupal\Component\Utility\Xss::filterAdmin(), which strips known XSS vectors while allowing a permissive list of HTML tags that are not XSS vectors. (I.e, and are not allowed.) See \Drupal\Component\Utility\Xss::$adminTags for the list of tags that will be allowed. If your markup needs any of the tags that are not in this whitelist, then you can implement a theme hook and template file and/or an asset library. Aternatively, you can use the render array key #allowed_tags to alter which tags are filtered.

As an alternative you may use FormattableMarkup:

'#markup' => new FormattableMarkup('<div><script src="http://localhost/project8/sites/all/libraries/test.js"></script></div>', []),

though it is not recommended in this case.