How to determine that there are no more products to show more?

Question

MODX

Hello, please tell me, I am working on one site and here I have such a task, loading new products using the "Show more" button is loaded by clicking on this button for 8 products, actually I did it, but the problem now is how determine that there are only 2 products in the "tiles" section, for example, and the "show more" button must be hidden then, because we have not even collected 8 products yet to show 8 more.
Here I just have 2 ajax requests, the first one is when we simply select a category, here is an ajax request and a screenshot, the categories are highlighted in red:

$.ajax({
      type: "POST",
      dataType: "html",
      url: "/assets/template/php/action.php",
      data: {"Id": IdElem},
      success: function(msg) {
        if(IdElem == 6 || IdElem == 11 || IdElem == 12 || IdElem == 13) {
          if(msg == "-1") {
            $(".contentBlock").empty();
            $(".contentBlock").append("<div class='col-md-12'><h3>К сожалению ничего не найдено<h3></div>");
            $(".fluiddBlock").css("display","none");
          }
          else {
            if($(".fluiddBlock").is(":hidden")) {
              $(".fluiddBlock").fadeIn(500);
            }
            if($("#filterBlock").is(":hidden")) {
              $("#filterBlock").removeAttr("style");
            }
            var heigthBlock = $(".contentBlock").outerHeight(true);
            $(".contentBlock").css("height",heigthBlock);
            $(".contentBlock").fadeOut(400,function() {
              $(".contentBlock").empty();
              $(".contentBlock").append(msg);
              $(".contentBlock").fadeIn(400,function() {
              heigthBlock = 0;
              $(".contentBlock").removeAttr("style");
              });
            });
          }
        }
        else {
          if(msg == "-1") {
            $(".contentBlock").empty();
            $(".contentBlock").append("<div class='col-md-12'><h3>К сожалению ничего не найдено<h3></div>");
            $(".fluiddBlock").css("display","none");
          }
          else {
            if($(".fluiddBlock").is(":hidden")) {
              $(".fluiddBlock").fadeIn(500);
            }
            $(".contentBlock").css("height",heigthBlock);
            $("#filterBlock, .contentBlock").fadeOut(400,function() {
              $(".contentBlock").empty();
              $(".contentBlock").append(msg);
              $(".contentBlock").fadeIn(400,function() {
              $(".contentBlock").removeAttr("style");
              });
            });
          }
        }
      }
    });

This is the action.php:

<?php 
/* include MODX_API BEGIN */
define('MODX_API_MODE', true);
require_once($_SERVER['DOCUMENT_ROOT'].'/index.php');
$modx=new modX();
$modx->initialize('web');
/* include MODX_API END */
$param = array(
  "tpl" => "tpl.msProducts.row2",
  "parents" => $_POST["Id"],
  "depth" => "0",
  "includeThumbs" => "medium",
  "sortby" => "pagetitle",
  "sortdir" => "ASC",
  "limit" => "8"
);
$output = $modx->runSnippet('msProducts',$param);
$modx->getParser()->processElementTags('', $output, false, false, '', array(), 10);
$modx->getParser()->processElementTags('', $output, true, true, '', array(), 10);
if(empty($output)) {
  echo "-1";
}
else {
  echo $output;
}

And the second ajax request is just the same by clicking on the "show more" button

$("#OpenNewItems").on("click",function() {
    var IdElem = $(".contentBlock")["0"].attributes.id.value;
    var currentObject = $(".ElemList");
    var currentLength = currentObject.length;
    $.ajax({
      type: "POST",
      dataType: "html",
      url: "/assets/template/php/actionNewItems.php",
      data: {"Id": IdElem, "currentElem": currentLength},
      success: function(msg) {
        if(msg == "-1") {
          $(".fluiddBlock").fadeOut(400);
        }
        else {
          $(".contentBlock").append(msg);
        }
      }
    });
    return false;
  });

This is actionNewItems.php:

<?php 
/* include MODX_API BEGIN */
define('MODX_API_MODE', true);
require_once($_SERVER['DOCUMENT_ROOT'].'/index.php');
$modx=new modX();
$modx->initialize('web');
/* include MODX_API END */
$param = array(
  "tpl" => "tpl.msProducts.row2",
  "limit" => "8",
  "offset" => $_POST["currentElem"],
  "parents" => $_POST["Id"],
  "depth" => "0",
  "includeThumbs" => "medium",
  "sortby" => "pagetitle",
  "sortdir" => "ASC",
);
$output = $modx->runSnippet('msProducts',$param);
$modx->getParser()->processElementTags('', $output, false, false, '', array(), 10);
$modx->getParser()->processElementTags('', $output, true, true, '', array(), 10);
if(empty($output)) {
  echo "-1";
}
else {
  echo $output;
}