<?php
/**
 * Defines the file entity class.
 *
 * @ContentEntityType(
 *   id = "file",
 *   label = @Translation("File"),
 *   controllers = {
 *     "storage" = "Drupal\file\FileStorage",
 *     "access" = "Drupal\file\FileAccessController",
 *     "view_builder" = "Drupal\Core\Entity\EntityViewBuilder"
 *   },
 *   base_table = "file_managed",
 *   entity_keys = {
 *     "id" = "fid",
 *     "label" = "filename",
 *     "uuid" = "uuid"
 *   }
 * )
 */

<?php
/**
 * Implements hook_entity_info().
 */
function user_entity_info() {
  $return = array(
    'user' => array(
      'label' => t('User'),
      'controller class' => 'UserController',
      'base table' => 'users',
      'uri callback' => 'user_uri',
      'label callback' => 'format_username',
      'fieldable' => TRUE,
      // $user->language is only the preferred user language for the user
      // interface textual elements. As it is not necessarily related to the
      // language assigned to fields, we do not define it as the entity language
      // key.
      'entity keys' => array(
        'id' => 'uid',
      ),
      'bundles' => array(
        'user' => array(
          'label' => t('User'),
          'admin' => array(
            'path' => 'admin/config/people/accounts',
            'access arguments' => array('administer users'),
          ),
        ),
      ),
      'view modes' => array(
        'full' => array(
          'label' => t('User account'),
          'custom settings' => FALSE,
        ),
      ),
    ),
  );
  return $return;
}

<?php
/**
 * Defines the user entity class.
 *
 * The base table name here is plural, despite Drupal table naming standards,
 * because "user" is a reserved word in many databases.
 *
 * @ContentEntityType(
 *   id = "user",
 *   label = @Translation("User"),
 *   controllers = {
 *     "storage" = "Drupal\user\UserStorage",
 *     "access" = "Drupal\user\UserAccessController",
 *     "list_builder" = "Drupal\user\UserListBuilder",
 *     "view_builder" = "Drupal\Core\Entity\EntityViewBuilder",
 *     "form" = {
 *       "default" = "Drupal\user\ProfileForm",
 *       "cancel" = "Drupal\user\Form\UserCancelForm",
 *       "register" = "Drupal\user\RegisterForm"
 *     },
 *     "translation" = "Drupal\user\ProfileTranslationHandler"
 *   },
 *   admin_permission = "administer user",
 *   base_table = "users",
 *   label_callback = "user_format_name",
 *   fieldable = TRUE,
 *   translatable = TRUE,
 *   entity_keys = {
 *     "id" = "uid",
 *     "uuid" = "uuid"
 *   },
 *   links = {
 *     "canonical" = "user.view",
 *     "edit-form" = "user.edit",
 *     "admin-form" = "user.account_settings",
 *     "cancel-form" = "user.cancel"
 *   }
 * )
 */
class User extends ContentEntityBase implements UserInterface {

/**
 * Implements hook_field_schema().
 */
function number_field_schema($field) {
  switch ($field['type']) {
    case 'number_integer' :
      $columns = array(
        'value' => array(
          'type' => 'int',
          'not null' => FALSE
        ),
      );
      break;

    case 'number_float' :
      $columns = array(
        'value' => array(
          'type' => 'float',
          'not null' => FALSE
        ),
      );
      break;

    case 'number_decimal' :
      $columns = array(
        'value' => array(
          'type' => 'numeric',
          'precision' => $field['settings']['precision'],
          'scale' => $field['settings']['scale'],
          'not null' => FALSE
        ),
      );
      break;
  }
  return array(
    'columns' => $columns,
  );
}

/**
 * Implements hook_field_info().
 */
function number_field_info() {
  return array(
    'number_integer' => array(
      'label' => t('Integer'),
      'description' => t('This field stores a number in the database as an integer.'),
      'instance_settings' => array('min' => '', 'max' => '', 'prefix' => '', 'suffix' => ''),
      'default_widget' => 'number',
      'default_formatter' => 'number_integer',
    ),
    'number_decimal' => array(
      'label' => t('Decimal'),
      'description' => t('This field stores a number in the database in a fixed decimal format.'),
      'settings' => array('precision' => 10, 'scale' => 2, 'decimal_separator' => '.'),
      'instance_settings' => array('min' => '', 'max' => '', 'prefix' => '', 'suffix' => ''),
      'default_widget' => 'number',
      'default_formatter' => 'number_decimal',
    ),
    'number_float' => array(
      'label' => t('Float'),
      'description' => t('This field stores a number in the database in a floating point format.'),
      'settings' => array('decimal_separator' => '.'),
      'instance_settings' => array('min' => '', 'max' => '', 'prefix' => '', 'suffix' => ''),
      'default_widget' => 'number',
      'default_formatter' => 'number_decimal',
    ),
  );
}

<?php
/**
 * The integer data type.
 *
 * The plain value of an integer is a regular PHP integer. For setting the value
 * any PHP variable that casts to an integer may be passed.
 *
 * @DataType(
 *   id = "integer",
 *   label = @Translation("Integer")
 * )
 */
class Integer extends PrimitiveBase implements IntegerInterface {

  /**
   * {@inheritdoc}
   */
  public function getCastedValue() {
    return (int) $this->value;
  }
}

<?php
/**
 * Defines the 'integer' field type.
 *
 * @FieldType(
 *   id = "integer",
 *   label = @Translation("Number (integer)"),
 *   description = @Translation("This field stores a number in the database as an integer."),
 *   default_widget = "number",
 *   default_formatter = "number_integer"
 * )
 */
class IntegerItem extends NumericItemBase {

  /**
   * {@inheritdoc}
   */
  public static function defaultSettings() {
    return array(
      'unsigned' => FALSE,
    ) + parent::defaultSettings();
  }

  /**
   * {@inheritdoc}
   */
  public static function defaultInstanceSettings() {
    return array(
      'min' => '',
      'max' => '',
      'prefix' => '',
      'suffix' => '',
      // Valid size property values include: 'tiny', 'small', 'medium', 'normal'
      // and 'big'.
      'size' => 'normal',
    ) + parent::defaultInstanceSettings();
  }

  /**
   * {@inheritdoc}
   */
  public static function propertyDefinitions(FieldStorageDefinitionInterface $field_definition) {
    $properties['value'] = DataDefinition::create('integer')
      ->setLabel(t('Integer value'));

    return $properties;
  }

  /**
   * {@inheritdoc}
   */
  public function getConstraints() {
    $constraints = parent::getConstraints();

    // If this is an unsigned integer, add a validation constraint for the
    // integer to be positive.
    if ($this->getSetting('unsigned')) {
      $constraint_manager = \Drupal::typedDataManager()->getValidationConstraintManager();
      $constraints[] = $constraint_manager->create('ComplexData', array(
        'value' => array(
          'Range' => array(
            'min' => 0,
            'minMessage' => t('%name: The integer must be larger or equal to %min.', array(
              '%name' => $this->getFieldDefinition()->getLabel(),
              '%min' => 0,
            )),
          ),
        ),
      ));
    }

    return $constraints;
  }

  /**
   * {@inheritdoc}
   */
  public static function schema(FieldStorageDefinitionInterface $field_definition) {
    return array(
      'columns' => array(
        'value' => array(
          'type' => 'int',
          'not null' => FALSE,
          // Expose the 'unsigned' setting in the field item schema.
          'unsigned' => $field_definition->getSetting('unsigned'),
          // Expose the 'size' setting in the field item schema. For instance,
          // supply 'big' as a value to produce a 'bigint' type.
          'size' => $field_definition->getSetting('size'),
        ),
      ),
    );
  }

}

<?php
drupal_add_css(drupal_get_path('module', 'example') . '/css/example.css');

<?php
$example = array(
  '#attached' => array(
    'css' => array(
      drupal_get_path('module', 'example') . '/css/example.css' => array(),
    ),
  ),
);

<?php
drupal_add_js(drupal_get_path('module', 'example') . '/example.js');

<?php
$example = array(
  '#attached' => array(
    'js' => array(
      drupal_get_path('module', 'example') . '/js/example.js' => array(),
    ),
  ),
);

<?php
  // jQuery Form Plugin.
  $libraries['jquery.form'] = array(
    'title' => 'jQuery Form Plugin',
    'website' => 'http://malsup.com/jquery/form/',
    'version' => '3.39',
    'js' => array(
      'core/assets/vendor/jquery-form/jquery.form.js' => array(),
    ),
    'dependencies' => array(
      array('system', 'jquery'),
      array('system', 'jquery.cookie'),
    ),
  );

jquery.form:
  remote: https://github.com/malsup/form
  version: 3.39
  js:
    assets/vendor/jquery-form/jquery.form.js: {}
  dependencies:
    - core/jquery
    - core/jquery.cookie

<?php
drupal_add_library('example', 'drag-and-drop');

<?php
$example = array(
  '#attached' => array(
    'library' => array(
      'example/drag-and-drop',
    ),
  ),
);