AJAX IN MAGENTO2.HOW TO ADD information from form IN DATABASE?

I already have a form and controller action, that send data without using ajax.How to do it with AJAX? I would appreciate your help!

view/frontend/templates/reviews.phtml

                Nickname
                
                Text Review
                

                    
                        Submit Review
                    
    
    

Controller/Index/Save.php

< ?php

namespace TrainingReviewsControllerIndex;
use MagentoFrameworkAppActionContext;
use TrainingReviewsModelReviewsFactory;

class Save extends MagentoFrameworkAppActionAction
{

protected $_test;

public function __construct(
   Context $context,
ReviewsFactory $test
 ) {
$this->_test = $test;
parent::__construct($context);
 }
 public function execute()
{

$data = $this->getRequest()->getParams();
$test = $this->_test->create();
$test->setData($data);
if($test->save()){
    $this->messageManager->addSuccessMessage(__('You saved 
  review'));
  }else{
    $this->messageManager->addErrorMessage(__('Review was not 
saved.'));
}
$resultRedirect = $this->resultRedirectFactory->create();
$resultRedirect->setPath('reviews/index/index');
return $resultRedirect;
}
}

Controller/Index/Index.php

< ?php

namespace TrainingReviewsControllerIndex;

class Index extends MagentoFrameworkAppActionAction
{
public function execute()
{
$this->_view->loadLayout();
$this->_view->getLayout()->initMessages();
$this->_view->renderLayout();
  }
}