How to add JS file using theme file in Drupal 8 ?

Sometimes we add Jquery file by libraries.yml but if we want to add JS file by `.theme` file in drupal 8 so we will add <script> code in `hook_page_attachments_alter`.
There we will create a variable and put the script code and then add in $page['#attached']['html_head'][].
We will add #tag is script and pass the script code variable using this code of line..

\Drupal\Core\Render\Markup::create($javascript_header)
 
here $javascript_header is our script code variable.

Example:
<?php
function hook_page_attachments_alter(array &$page) {   
   
$javascript_header = 'var hmt = hmt || [];
(function()
{
var hm = document.createElement("script");
hm.src = "https://hm.baidu.com/hm.js?1236547890";
var s = document.getElementsByTagName("script")[0]; s.parentNode.insertBefore(hm, s);
}
 )();';
        $page['#attached']['html_head'][] = [       
            [       
              '#tag' => 'script',         
              '#value' => \Drupal\Core\Render\Markup::create($javascript_header),       
              '#weight' => -1,
            ],       
            'key'
        ];
   
}
?>
So this is simple way to add JS file in header of project of Drupal 8.

Note: If have any suggestions or issue regarding 'How to add JS file using theme file in Drupal 8 ?' then you can ask by comments.  

How to send email programmatically in Drupal 8?

Sometime we need to send email on any events or after creation of blog or article or in any e-commerce site for send confirmation mail after successful completion of order. So In this Blog we are going to explore how to send email programmatically in drupal 8.
We just have to use `hook_mail` function in '.module' file. here two simple steps for send email:

1. Define your properties like Subject, body, headers etc in hook_mail() function.
2. Use Mail Manager to send email.

When we need to send email programmatically, we need to specify the module name that implements hook_mail().
Now have a look of implementation.

<?php

/**
 * Implements hook_mail().
 */
function [module_name]_mail($key, &$message, $params) {
    $options = array(
        'langcode' => $message['langcode'],
    );
    $message['headers']['Content-Type'] = 'text/html; charset=UTF-8; format=flowed; delsp=yes';
    switch ($key) {
        case 'create_event':
            $message['from'] = \Drupal::config('system.site')->get('mail');
            $message['subject'] = t('Notification: @subject', array('@subject' => $params['subject']), $options);
            $message['body'][] = SafeMarkup::checkPlain($params['message']);
            break;
    }
}
?>

Here $key is defines one template identified as test_message.
The two other arguments are $params and $message. here $parms is an array of data that needs to go in the email and that is passed from mail manager.
So here is final step for send mail via `mailManager`.

<?php
/**
* Implements hook_entity_insert().
*/
function [module_name]_entity_insert(Drupal\Core\Entity\EntityInterface $entity) {
    if ($entity->getEntityTypeId() !== 'node' || ($entity->getEntityTypeId() === 'node' && $entity->bundle() !== 'event')) {
      return;
    }   
    $user_email = \Drupal::currentUser()->getEmail();
    $key = 'create_event';
    $module = <module_name>;
    // mail sending to reviewer users
    $msg1 = "Hello, <br /><br />";
    $msg1.= "Please check your content item, that is published by publisher.";
    $msg1.= "Kind regards";

    $mailManager = \Drupal::service('plugin.manager.mail');
    $to = $user_email;
    $params['message'] = t($msg1);
    $params['subject'] = "Project name workflow for published Notification.";
    $langcode = \Drupal::currentUser()->getPreferredLangcode();
    $send = true;

    $result = $mailManager->mail($module, $key, $to, $langcode, $params, NULL, $send);   

    if ($result['result'] !== true) {
      drupal_set_message(t('There was a problem sending your message.'), 'error');
    }
    else {
      drupal_set_message(t('Your message has been sent.'));
    }   
}
?>

By default, PHPMail, which is use for default_mail() function in PHP. So this will triggered whenever any event will be created, here
$send = the boolean value which is indicating whether the email should be actually sent or not.
$key = template id.


Note: If have any suggestions or issue regarding 'How to send email programmatically in Drupal 8?' then you can ask by comments.  
   

How to upload file using URL in drupal 8 programmatically?

Here is a simple way to upload file either file or image by URL in drupal 8. We are going to give an example for this query.
Example: First we need an url like..
        $fileurl = $fileurlval->url;             
        $name = str_replace(' ', '-', strtolower($meta_title).'.pdf');   //here meta_title is the name of your pdf or image
       
        //Get the uploaded file from the url.  
        $filedata = file_get_contents($fileurl);
       
        //Saves a file to the specified destination and creates a database entry.
        $file_directory_name = 'images'; // it means  upload folder name  
        $uploaded_file = file_save_data($filedata, "public://".$file_directory_name."/".$name, FILE_EXISTS_RENAME);
       
        // here "public://" means 'sites/default/files/' folder..
        // here $file_directory_name means we can set any folder where we want to upload..
        // here $name is name of file name..
                           
        if (!empty($uploaded_file)) { 
            $file_arr = array(
                "target_id" => $uploaded_file->id(),
                 "alt" => $uploaded_file->getFilename(),
            );       
       
            $node->field_resources_asset_tagging = $file_arr; // here field_resources_asset_tagging is file field..       
        }

So this is the way to upload file/image in drupal 8 programmatically.  


Note: If have any suggestions or issue regarding 'How to upload file using URL in drupal 8 programmatically?' then you can ask by comments.  
   

How to remove or unset META tag from web page?

If we want to hide or unset or remove META Tag from our web page then we have to use `hook_page_attachments_alter` in `.theme` file.
we have to create an array and pass the name of `META name` which we want to remove or unset from web page.
like..
$unset_meta = [
    'title', // Meta name "title"
    'description', // Meta name "description"
    'keywords', // Meta name "keywords"
    'Generator'     // Meta name "Generator"
];

then with the help of $page['#attached']['html_head'], page attachments html_head we have to check that meta name if exist then we have to unset this.
we are giving here an example for this..

Example:
function moldev_page_attachments_alter(array &$page) { // here moldev is my theme name.
 // Define an array of META tags to remove.
   $unset_meta = [
    'title', // Meta name "title" 
    'description', // Meta name "description"
    'keywords', // Meta name "keywords"
    'Generator'     // Meta name "Generator"   
   ];
  // Check values and delete.
   foreach ($page['#attached']['html_head'] as $key => $value) {
     if (in_array($value[1], $unset_meta)) unset($page['#attached']['html_head'][$key]);
   }
}

if you want to delete/remove/unset any link rel="alternate" and hreflang="en" or any language then follow the below given code.
foreach ($page['#attached']['html_head_link'] as $key => $attachment) {   
          if ($attachment[0]['rel'] == 'alternate' && $attachment[0]['hreflang'] == 'en') {
               unset($page['#attached']['html_head_link'][$key]);
          }
}

Note: If have any suggestions or issue regarding 'How to remove or unset META tag from web page?' then you can ask by comments.  

How to create Schema in custom module drupal 8?

When we need to create our custom module table, So we have to create schema file in custom module root like if our module name is `crudform`, so in the folder of module we will create file which name is `crudform.install`. here our file extension will be `.install` for schema.
In the file we will create function `hook_schema()` with name of `crudform_schema()` and there we will define create structure of table with table name, we have an example for this, Please have a look..

Schema database

function crudform_schema() {
  $schema['crudform'] = array(
    'fields' => array(
          'id'=>array(
            'type'=>'serial',
            'not null' => TRUE,
          ),
          'name'=>array(
            'type' => 'varchar',
            'length' => 40,
            'not null' => TRUE,
          ),
           'email'=>array(
            'type' => 'varchar',
            'length' => 255,
            'not null' => TRUE,
          ),
            'city'=>array(
            'type' => 'varchar',
            'length' => 255,
            'not null' => TRUE,
          ),
            'country'=>array(
            'type' => 'varchar',
            'length' => 255,
            'not null' => TRUE,
          ),
          'message'=>array(
            'type' => 'varchar',
            'length' => 255,
            'not null' => TRUE,
          ),
    ),
    'primary key' => array('id'),
  );
  return $schema;
}

In that function crudform_schema(), our database table name will be `crudform`. here we will define table fields and structure and then return the schema. When we will install our custom module then this table with schema will automatically create in database and with the help of this we can store data in our custom table.


If we want to store default data on table then we have to use `hook_install` function In case of installation of module that data will store automatically. We have an example for this, please have a look..

function crudform_install() {
  $database = \Drupal::database();
  // Add default entry in table.
  $fields = array(
    'name' => 'Sahil',
    'email' => 'sahil@gmail.com',
    'city' => 'Delhi',
    'country' => 'India',
    'message' => 'Hello text',
  );
  $database->insert('crudform')
    ->fields($fields)
    ->execute();
  
  // Add one another entry on this table.
  $fields = array(
    'name' => 'Abhi',
    'email' => 'abhi@gmail.com',
    'city' => 'Delhi',
    'country' => 'India',
    'message' => 'Hello text world',
  );
  $database->insert('crudform')
    ->fields($fields)
    ->execute();
}

There we are creating a $fields array with few data and then store by insert query.
So that's a simple process of 'create schema in drupal 8 custom module'.


Note: If have any suggestions or issue regarding 'How to create Schema in custom module drupal 8?' then you can ask by comments.   

What is right query structure for drupal 8?

Here we are defining our drupal 8 query structure with easy mode. You can find/search here INSERT, SELECT, UPDATE, DELETE.
We will explain in easy way with an examples, Please have a look..
That is our table `testing_form` structure..

id	candidate_name	candidate_mail	candidate_number	candidate_dob
1	John	john@gmail.com	1236547890	2014-10-22
2	Mary	mary@gmail.com	5698741230	2014-10-23
3	Karen	karen@gmail.com	0123654789	2014-10-23

INSERT Query Structure:
According to php we will define INSERT Query as:

$insert_query = "INSERT INTO testing_form (candidate_name, candidate_mail, candidate_number, candidate_dob) VALUES ('sahil', 'sahil@gmail.com', '9874563210', '22-11-1990')";
mysqli_query($connection, $insert_query);

And now in case of drupal 8, our structure will be.

$fields = array(
    'candidate_name'   => 'sahil',
    'candidate_mail'   => 'sahil@gmail.com',
    'candidate_number' => '9874563210' ,
    'candidate_dob'    => '22-11-1990',           
);
db_insert('testing_form')
    ->fields($fields)
    ->execute();
   
Here 'testing_form' is table name and $fields variable is the data for fields of table.


SELECT Query Structure:
According to php we will define SELECT Query as:

$select_query = "SELECT * from testing_form where id = '2' and id != '3'";
mysqli_query($connection, $select_query);

And now in case of drupal 8, our structure will be.

$result = db_select('testing_form', 't')
    ->fields('t')
    ->condition('id', 2, '=')
    ->condition('id', 3, '!=')
    ->execute()
    ->fetchAll();
   
Here 'testing_form' is table name and our condition is all 2nd id candidate come but not come on 3rd id candidate.

We have some other method for SELECT query with connection in drupal 8..

$connection = \Drupal\Core\Database\Database::getConnection();
$results = $connection->query('select candidate_name, candidate_mail, candidate_number, candidate_dob')->fetchAll();


UPDATE Query Structure:
According to php we will define UPDATE Query as:

$update_query = "UPDATE `testing_form` set candidate_name='karen sood' where id='3'";
mysqli_query($connection, $update_query);

And now in case of drupal 8, our structure will be.

$update_query = \Drupal::database()->update('testing_form')
          ->fields(array('candidate_name' => 'karen sood', 'candidate_number' => '1236547890'))
          ->condition('id', '3')         
          ->execute();
   
Here 'testing_form' is table name and our condition is id number `2nd` of candidate data will update.

 
DELETE Query Structure:
According to php we will define DELETE Query as:

$delete_query = "DELETE from `testing_form` where id='3'";
mysqli_query($connection, $delete_query);

And now in case of drupal 8, our structure will be.

$delete_query = \Drupal::database()->delete('testing_form');
      ->condition('id', '3');   
      ->execute();
   
Here 'testing_form' is table name and our condition is id number `3rd` of candidate data will delete.


So these all are INSERT, SELECT, UPDATE, DELETE queries structure for Drupal 8. Next time we will come with `JOINS`, like how to use `joins` in drupal 8 query with many of conditions.



Note: If have any suggestions or issue regarding 'What is right query structure for drupal 8?' then you can ask by comments.  

Steps for Add Custom or Add More Language on website.

If we want to add custom language or add multiple languages on our drupal website then we have to add and install `Language Module` first.

Install Language module

Then click on the Configure link or go with this link "/admin/config/regional/language".

Language List

and then you can add custom language by choose last option "Custom Language". After choose you will be redirect in this page.

Choose Custom or other language option

If we are choosing default languages that given by module then automatically will be added on list, but in case of last option custom language we will reach in this page.

Set Custom language code and name

After this you will redirect to listing page of added languages.

Language list

here we can set our default language that will automatically display in language list.

After that we have to check the "Show language selector on create and edit pages" option on content type edit page in "language settings".

Content type edit page for add dropdown option

Then you will be get the language drop-down in body/description type fields on node form.
So this is the simple steps for Add Custom or Add more language in website.



Note: If have any suggestions or issue regarding 'Steps for Add Custom or Add More Language on website.' then you can ask by comments.