Scrolling works on desktop not on mobile devices

Question

This is what i have and it's working fine on desktop but on mobile it dosent seme to load

      windowOnScroll();
});
function windowOnScroll() {
     $(window).on("scroll", function(e){
      if ($(window).scrollTop() == $(document).height() - $(window).height()){
          if($(".post-item").length < $("#total_count").val()) {
              var lastId = $(".post-item:last").attr("id");
              getMoreData(lastId);
          }
      }
  });
}

  function getMoreData(lastId) {-
     $(window).off("scroll");
  $.ajax({
      url: 'getMoreData.php?lastId=' + lastId,
      type: "get",
      beforeSend: function ()
      {
          $('.ajax-loader').show();
      },
      success: function (data) {
             setTimeout(function() {
              $('.ajax-loader').hide();
          $("#post-list").append(data);
          windowOnScroll();
             }, 1000);
      }
 });
}

It works just fine on desktop but on mobile dosen't work at all.