1<!-- Semantic HTML5 Elements -->
2<header> - Page/section header
3<nav>    - Navigation section
4<main>   - Main content area
5<article>- Self-contained content
6<aside>  - Sidebar content
7<footer> - Page/section footer

1.container {
2  display: flex;
3  justify-content: center;  /* Main axis */
4  align-items: center;      /* Cross axis */
5  flex-wrap: wrap;
6}

1// Variable declarations
2const CONSTANT = "Cannot reassign";  // Block-scoped, immutable
3let mutable = "Can reassign";        // Block-scoped, mutable
4var legacy = "Function-scoped";      // Avoid in modern JS
5
6// Arrow functions
7const greet = (name) => `Hello, ${name}`;
8
9// Promises
10fetch('/api/data')
11  .then(response => response.json())
12  .then(data => console.log(data))
13  .catch(error => console.error(error));
14
15// DOM manipulation
16document.addEventListener('DOMContentLoaded', function() {
17  const element = document.getElementById('myId');
18  element.addEventListener('click', handler);
19});
20
21// jQuery equivalent
22$(document).ready(function() {
23  $('#myId').on('click', handler);
24});

1Vocabulary (container)
2└── Terms (items)
3    ├── Parent term
4    │   ├── Child term
5    │   └── Child term
6    └── Another term

1# Export config
2drush config:export   # or drush cex
3
4# Import config
5drush config:import   # or drush cim
6
7# Single config export
8drush config:get system.site
9
10# Rebuild cache
11drush cache:rebuild   # or drush cr

1themes/custom/mytheme/
2├── mytheme.info.yml          # Required: Theme metadata
3├── mytheme.libraries.yml      # CSS/JS libraries
4├── mytheme.theme              # PHP preprocess functions
5├── mytheme.breakpoints.yml    # Responsive breakpoints
6├── config/
7│   └── install/
8│       └── mytheme.settings.yml
9├── css/
10│   └── style.css
11├── js/
12│   └── scripts.js
13├── templates/                 # Twig template overrides
14│   ├── page.html.twig
15│   └── node--article.html.twig
16└── logo.svg

1# mytheme.info.yml
2name: My Theme
3type: theme
4description: 'A custom Drupal theme'
5core_version_requirement: ^10 || ^11
6base theme: starterkit_theme  # or 'false' for no base
7
8libraries:
9  - mytheme/global
10
11regions:
12  header: 'Header'
13  content: 'Content'
14  sidebar: 'Sidebar'
15  footer: 'Footer'

1# mytheme.libraries.yml
2global:
3  version: 1.0
4  css:
5    theme:
6      css/style.css: {}
7  js:
8    js/scripts.js: {}
9  dependencies:
10    - core/jquery
11    - core/drupal
12
13slider:
14  css:
15    component:
16      css/slider.css: {}
17  js:
18    js/slider.js: {}

1{# Comment - not rendered #}
2
3{{ variable }}                    {# Output #}
4{{ variable|filter }}             {# Apply filter #}
5{% if condition %}...{% endif %}  {# Control structure #}
6
7{# Common Filters #}
8{{ title|upper }}                 {# Uppercase #}
9{{ body|raw }}                    {# Output raw HTML (careful!) #}
10{{ "Hello"|t }}                   {# Translation #}
11{{ items|length }}                {# Count items #}
12{{ date|date("Y-m-d") }}          {# Format date #}
13
14{# Control Structures #}
15{% if user.logged_in %}
16  Welcome, {{ user.name }}
17{% else %}
18  Please log in
19{% endif %}
20
21{% for item in items %}
22  {{ item.title }}
23{% empty %}
24  No items found
25{% endfor %}
26
27{# Including Templates #}
28{% include 'partial.html.twig' %}
29{% include 'partial.html.twig' with {'title': 'Hello'} %}
30
31{# Template Inheritance #}
32{% extends 'base.html.twig' %}
33{% block content %}...{% endblock %}
34
35{# Drupal-specific #}
36{{ attach_library('mytheme/slider') }}
37{{ content|without('field_image') }}

1# development.services.yml
2parameters:
3  twig.config:
4    debug: true
5    cache: false

1node.html.twig                    # All nodes
2node--article.html.twig           # Article content type
3node--article--teaser.html.twig   # Article teaser view
4node--123.html.twig               # Specific node ID
5
6field.html.twig                   # All fields
7field--body.html.twig             # Body field
8field--node--body.html.twig       # Body field on nodes
9
10block.html.twig                   # All blocks
11block--system-branding-block.html.twig

1// mytheme.theme
2
3/**
4 * Implements hook_preprocess_HOOK() for page templates.
5 */
6function mytheme_preprocess_page(&$variables) {
7  $variables['my_custom_var'] = 'Hello World';
8}
9
10/**
11 * Implements hook_preprocess_HOOK() for node templates.
12 */
13function mytheme_preprocess_node(&$variables) {
14  $node = $variables['node'];
15  
16  // Add variable for specific content type
17  if ($node->bundle() === 'article') {
18    $variables['is_article'] = TRUE;
19  }
20}
21
22/**
23 * Implements hook_theme_suggestions_HOOK_alter().
24 */
25function mytheme_theme_suggestions_node_alter(array &$suggestions, array $variables) {
26  $node = $variables['elements']['#node'];
27  // Add custom suggestion based on field value
28  if ($node->hasField('field_layout')) {
29    $suggestions[] = 'node__' . $node->field_layout->value;
30  }
31}

1{# Default attributes #}
2<div{{ attributes }}>
3
4{# Add classes #}
5<div{{ attributes.addClass('my-class', 'another-class') }}>
6
7{# Remove class #}
8<div{{ attributes.removeClass('unwanted') }}>
9
10{# Set attribute #}
11<div{{ attributes.setAttribute('data-id', node.id) }}>
12
13{# Check if has class #}
14{% if attributes.hasClass('active') %}

1modules/custom/mymodule/
2├── mymodule.info.yml           # Required: Module metadata
3├── mymodule.module             # Hooks and procedural code
4├── mymodule.install            # Install/update hooks
5├── mymodule.routing.yml        # URL routes
6├── mymodule.services.yml       # Service definitions
7├── mymodule.permissions.yml    # Permissions
8├── mymodule.libraries.yml      # Frontend assets
9├── config/
10│   ├── install/                # Default config
11│   └── schema/                 # Config schema
12├── src/
13│   ├── Controller/             # Page controllers
14│   ├── Form/                   # Form classes
15│   ├── Plugin/                 # Plugin classes
16│   │   └── Block/              # Custom blocks
17│   ├── Service/                # Service classes
18│   └── EventSubscriber/        # Event subscribers
19└── templates/                  # Module templates

1# mymodule.info.yml
2name: My Module
3type: module
4description: 'Module description'
5core_version_requirement: ^10 || ^11
6package: Custom
7
8dependencies:
9  - drupal:node
10  - drupal:views

1# mymodule.routing.yml
2mymodule.my_page:
3  path: '/my-path/{node}'
4  defaults:
5    _controller: '\Drupal\mymodule\Controller\MyController::content'
6    _title: 'My Page'
7  requirements:
8    _permission: 'access content'
9    node: \d+
10  options:
11    parameters:
12      node:
13        type: entity:node

1# mymodule.services.yml
2services:
3  mymodule.my_service:
4    class: Drupal\mymodule\Service\MyService
5    arguments: ['@entity_type.manager', '@current_user']
6    
7  mymodule.event_subscriber:
8    class: Drupal\mymodule\EventSubscriber\MySubscriber
9    tags:
10      - { name: event_subscriber }

1<?php
2namespace Drupal\mymodule\Controller;
3
4use Drupal\Core\Controller\ControllerBase;
5use Drupal\node\NodeInterface;
6
7class MyController extends ControllerBase {
8
9  public function content(NodeInterface $node) {
10    return [
11      '#theme' => 'my_template',
12      '#node' => $node,
13      '#cache' => [
14        'tags' => $node->getCacheTags(),
15      ],
16    ];
17  }
18}

1<?php
2namespace Drupal\mymodule\Form;
3
4use Drupal\Core\Form\FormBase;
5use Drupal\Core\Form\FormStateInterface;
6
7class MyForm extends FormBase {
8
9  public function getFormId() {
10    return 'mymodule_my_form';
11  }
12
13  public function buildForm(array $form, FormStateInterface $form_state) {
14    $form['name'] = [
15      '#type' => 'textfield',
16      '#title' => $this->t('Name'),
17      '#required' => TRUE,
18    ];
19    
20    $form['submit'] = [
21      '#type' => 'submit',
22      '#value' => $this->t('Submit'),
23    ];
24    
25    return $form;
26  }
27
28  public function validateForm(array &$form, FormStateInterface $form_state) {
29    if (strlen($form_state->getValue('name')) < 3) {
30      $form_state->setErrorByName('name', $this->t('Name must be at least 3 characters.'));
31    }
32  }
33
34  public function submitForm(array &$form, FormStateInterface $form_state) {
35    $this->messenger()->addMessage($this->t('Hello, @name!', [
36      '@name' => $form_state->getValue('name'),
37    ]));
38  }
39}

1// Load entities
2$node = Node::load($nid);
3$nodes = Node::loadMultiple([1, 2, 3]);
4
5// Entity query
6$nids = \Drupal::entityQuery('node')
7  ->condition('type', 'article')
8  ->condition('status', 1)
9  ->sort('created', 'DESC')
10  ->range(0, 10)
11  ->accessCheck(TRUE)
12  ->execute();
13
14// Entity type manager
15$storage = \Drupal::entityTypeManager()->getStorage('node');
16$node = $storage->load($nid);
17
18// Create entity
19$node = Node::create([
20  'type' => 'article',
21  'title' => 'My Title',
22]);
23$node->save();
24
25// Field access
26$title = $node->getTitle();          // or $node->label()
27$body = $node->get('body')->value;
28$node->set('field_name', 'value');

1// Select query
2$results = \Drupal::database()->select('node_field_data', 'n')
3  ->fields('n', ['nid', 'title'])
4  ->condition('type', 'article')
5  ->condition('status', 1)
6  ->orderBy('created', 'DESC')
7  ->range(0, 10)
8  ->execute()
9  ->fetchAll();
10
11// Insert
12\Drupal::database()->insert('mytable')
13  ->fields(['name' => 'value'])
14  ->execute();
15
16// Update
17\Drupal::database()->update('mytable')
18  ->fields(['name' => 'new_value'])
19  ->condition('id', 1)
20  ->execute();
21
22// Delete
23\Drupal::database()->delete('mytable')
24  ->condition('id', 1)
25  ->execute();

1// Current user
2$account = \Drupal::currentUser();
3$uid = $account->id();
4$is_admin = $account->hasPermission('administer site configuration');
5
6// Entity type manager
7$storage = \Drupal::entityTypeManager()->getStorage('node');
8
9// Config
10$config = \Drupal::config('system.site');
11$site_name = $config->get('name');
12
13// Editable config
14$config = \Drupal::configFactory()->getEditable('mymodule.settings');
15$config->set('my_setting', 'value')->save();
16
17// State API (environment-specific values)
18$last_run = \Drupal::state()->get('mymodule.last_run');
19\Drupal::state()->set('mymodule.last_run', time());
20
21// Logger
22\Drupal::logger('mymodule')->error('Error message: @error', [
23  '@error' => $error_message,
24]);
25
26// Messenger
27\Drupal::messenger()->addStatus('Success!');
28\Drupal::messenger()->addWarning('Warning!');
29\Drupal::messenger()->addError('Error!');
30
31// Cache
32$cache = \Drupal::cache();
33$item = $cache->get('my_cache_key');
34$cache->set('my_cache_key', $data, Cache::PERMANENT, ['node:1']);

1// NEVER do this
2echo $user_input;  // XSS vulnerability!
3$query = "SELECT * FROM users WHERE id = $user_id";  // SQL injection!
4
5// DO this instead
6use Drupal\Component\Utility\Html;
7use Drupal\Component\Utility\Xss;
8
9// Escape output
10$safe = Html::escape($user_input);
11
12// Filter HTML (allows some tags)
13$filtered = Xss::filter($user_input);
14
15// Database placeholders (automatic escaping)
16$result = \Drupal::database()->query(
17  'SELECT * FROM {users} WHERE uid = :uid',
18  [':uid' => $user_id]
19);
20
21// Check access
22if ($node->access('view')) { ... }
23if ($account->hasPermission('administer nodes')) { ... }

1/**
2 * Implements hook_help().
3 */
4function mymodule_help($route_name, $route_match) {
5  if ($route_name === 'help.page.mymodule') {
6    return '<p>' . t('Help text here.') . '</p>';
7  }
8}
9
10/**
11 * Implements hook_cron().
12 */
13function mymodule_cron() {
14  // Run periodic tasks
15}
16
17/**
18 * Implements hook_ENTITY_TYPE_presave().
19 */
20function mymodule_node_presave(NodeInterface $node) {
21  // Modify node before saving
22}
23
24/**
25 * Implements hook_ENTITY_TYPE_insert().
26 */
27function mymodule_node_insert(NodeInterface $node) {
28  // React after node is created
29}
30
31/**
32 * Implements hook_form_alter().
33 */
34function mymodule_form_alter(&$form, FormStateInterface $form_state, $form_id) {
35  // Modify any form
36}
37
38/**
39 * Implements hook_form_FORM_ID_alter().
40 */
41function mymodule_form_node_article_edit_form_alter(&$form, FormStateInterface $form_state, $form_id) {
42  // Modify specific form
43}

1// Unit Test - No Drupal bootstrap
2namespace Drupal\Tests\mymodule\Unit;
3
4use Drupal\Tests\UnitTestCase;
5
6class MyUnitTest extends UnitTestCase {
7  public function testSomething() {
8    $this->assertEquals(1, 1);
9  }
10}
11
12// Kernel Test - Minimal Drupal
13namespace Drupal\Tests\mymodule\Kernel;
14
15use Drupal\KernelTests\KernelTestBase;
16
17class MyKernelTest extends KernelTestBase {
18  protected static $modules = ['mymodule'];
19  
20  public function testSomething() {
21    // Has database access
22  }
23}
24
25// Functional Test - Full Drupal
26namespace Drupal\Tests\mymodule\Functional;
27
28use Drupal\Tests\BrowserTestBase;
29
30class MyFunctionalTest extends BrowserTestBase {
31  protected static $modules = ['mymodule'];
32  protected $defaultTheme = 'stark';
33  
34  public function testSomething() {
35    $this->drupalGet('/my-path');
36    $this->assertSession()->statusCodeEquals(200);
37  }
38}

1# Cache
2drush cr                    # Clear all caches
3drush cc render             # Clear specific cache bin
4
5# Config
6drush cex                   # Export configuration
7drush cim                   # Import configuration
8drush cget system.site      # View config item
9
10# Database
11drush sql-cli               # Open database CLI
12drush sql-dump > backup.sql # Export database
13drush sql-query "SELECT..."  # Run query
14
15# User
16drush user:create username --mail="email@test.com"
17drush user:password username newpass
18drush user:role:add administrator username
19
20# Modules
21drush pm:list               # List modules
22drush pm:enable mymodule    # Enable module
23drush pm:uninstall mymodule # Uninstall module
24
25# Updates
26drush updb                  # Run database updates
27drush updatedb:status       # Check pending updates
28
29# Queue
30drush queue:list            # List queues
31drush queue:run myqueue     # Process queue

1drush cr         # Clear cache (most used!)
2drush cex        # Export config
3drush cim        # Import config
4drush updb       # Database updates
5drush uli        # Generate login link