News filter using RestartBuffer does not work correctly. What could be the reason?

Question

1C-Bitrix

Good afternoon.
This is the first time I've encountered ajax content substitution, I've always done just get parameters in the url.
The problem is this:
1. before calling the news component, I wrote the following:

if ($_GET['_ajax'] == 'y') {
                $GLOBALS['APPLICATION']->RestartBuffer();
}

2. After component:

if ($_GET['_ajax'] == 'y') {
   die();
}

js script:

$('.portfolio--filter a').click(function(){
    $('.portfolio--filter a').removeClass('active-link');
    $(this).addClass('active-link');
    let url = $(this).attr('href')+'?_ajax=y';
    $.ajax({
    url:     url,
    type:     "GET",
    success: function(response) {
      $('#portfolio-wrapper').html(response);
    },
    error: function(jqXHR, textStatus, errorThrown){ 
      console.log('Error: '+ errorThrown);
    }
  });
  return false;
})

The filter itself works, but the problem is that the entire page of the site is inserted into the content area.

Answer 1

Try to substitute this flag in the component parameters so that it is taken into account in the cache key
'IS_AJAX' => $_GET['_ajax']
your component has already worked and cached, so the code is not re-executed
Why don't you want the Ajax mode built into Bitrix for components to use?