Usually in ReactJS project, we create many components and these components are objects having their presentation and behaviour logic written within their definition. A component is visual object with some behaviour and the visual part is defined using the JSX or HTML with CSS styles and behaviour is created using life cycle functions, event handling and state object.

You can use this script to setup PHP environment with apache server having all required modules for running your project.

Here are some webform hooks which execute before rendering form. These hooks can manipulate form appearance and elements values.

function webform_webform_submission_prepare_form(WebformSubmissionInterface $webform_submission, $operation, FormStateInterface $form_state) {

}


function custom_form_alter(&$form, FormStateInterface $form_state, $form_id) { 
      $form["elements"]["full_name"]["#title"]='New Title';
} 



function custom_preprocess_webform(&$variables) {

}

Sometime, we need to intercept the values being submitted by website and want to execution our code for these values like sending them to API or submitting them third party URL.

So, webform module gives you freedom to write your code code then may execute at different events of webform submit.

For this, Just create a module and add your code as a plugin.

Steps to create custom webform handler:

1 . Create module: create a module named as "custom"

custom.info.yml

In Drupal 8, most of the work can be done without writing any code but there may be situation where you want to write your logic and then want to send the output of that logic to view.

Here, we are using custom module where we have various hook function available  to write login inside their  body and where you can add your value to final output. Most of the function has parameter &$variables which is the reference of $variables variable to be rendered by drupal to produce final output.

Here is the module structure :

In Drupal 8, sometime we need to write custom code and output of this custom code to be sent to frontend templates for rendering. Here, we can write the custom code in module but I am writing custom code in *.theme file which has one mytheme_preprocessor function and I want to send a value for rendering in template.

Here is the example

function mytheme_preprocess(&$variables) {
  $variables['myname'] = 'Jone Doe';
}

And you can access this value in twig file like given below

{{myname}}

There may be requirement when you need to link the contents from different nodes to a specific node. For example, you may want to allow user a facility that they can set the related content from different nodes in a page like we do in ecommerce portal where we configure related products.

This can be achieved in drupal 8 in following steps:

1. the a field of type content
2. select the node type you want to link with
3. select how many related node you want to configure in this newly created field
4. and save then.

This is how we add persistence storage to container that can be used by application running in container. You can create volume like drive in windows OS which can be treated by Kubernetes  like hard disk. This volume can be mounted to pod to create storage with containers running in cluster.

Kubernetes allows you to declare entry point command to be executed when container will be created first. This is very similar to Dockerfile CMD option where we can write a command that will start our service, server or application whenever new container will be created using the image built with this docker file.

Here is the example to expose internal services to the out side world.