Code

Form API :

$form['the_text_field']['#attributes']['class'][] = 'ctools-auto-submit-exclude';

OR

'#attributes' => array('class' => array('ctools-auto-submit-exclude')),

Views (using hook_form_alter)

This is a drupal 8 contrib module allow  you (developer) to find code examples.

Drupal Tutorial : https://www.drupal.org/simpletest

Example :

# Add a new CSS file:

stylesheets:

  all:

    - layout.css

Example:

Site Name:    

$site_name = \Drupal::config('system.site')->get('name');

 

Site Address (Host)

$site_addr = "http://" . \Drupal::request()->getHost();

In drupal 8 block is part of the plugin system.

Step 1. Create a simple module like this.

Example : (Insert this line in to your form submitForm() methode)

Redirect to the user page ( Redirection on form submit)

$form_state->setRedirect('user.page');

Example :  Display user login form on a page

Step 1:  Create a module. (Example)