In Drupal 8 what is the process for creating blocks with html and javascript?

Here is my sample code for creating the block

class TopNewsBlock extends BlockBase {

   * {@inheritdoc}
  public function build() {
     //Fetch data
     return array(
      'type' => 'markup',
      '#markup' => '<table id="example_table"></table>',
      '#attached' => array(
        'library' =>  array(      


It works but the problem I have is - I want to seperate out the html code from the php code. Is it possible to include a html file within the block just like the way a javascript file is attached as a library?

1 Answer 1


You need to use hook_theme() in your module, and declare a new Twig template that you want to use for your block.

Here's an example that needs to go to YOUR_MODULE.module file:

function YOUR_MODULE_theme() {
  return [
      // Here you can pass any variables you want, if necessary.
      'variables' => ['var1' => NULL],

Then create a folder called /templates in your custom module, and YOUR_TEMPLATE_KEY.html.twig file where you can have any markup you want. See below how to use the variables you pass to the template:

<div id="your-block">
  {{ var1 }}

Finally, to use it:

public function build() {
  return [
    '#theme' => 'YOUR_TEMPLATE_KEY',
    '#var1' => 'Variable one passed here',

Hope this helps.

  • I get the error Template "modules/custom/MY_MODULE_NAME/templates/MY_TEMPLATE_NAME.html.twig" is not defined (Drupal\Core\Template\Loader\ThemeRegistryLoader: Unable to find template "modules/custom/MY_MODULE_NAME/templates/MY_TEMPLATE_NAME.html.twig" in the Drupal theme registry.
    – Bhuvana
    Mar 4, 2016 at 11:01
  • Did you clear caches? Mar 4, 2016 at 11:01
  • Yes. I uninstalled and reinstalled the module as well. Didnt help.
    – Bhuvana
    Mar 4, 2016 at 11:02
  • Strange; I tested the code above before posting and it worked well. Make sure that all naming is correct and that there are no typos. Mar 4, 2016 at 11:02
  • 1
    The code is correct.
    – user21641
    Mar 4, 2016 at 12:01

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