Call function on scroll only once

Question

I got a question regarding a function that will be called if the object is within my screen. But when the object is within my screen the function is been called and a alert

Answer 1

$(window).on('scroll', function() {
  if ($(document).scrollTop() >= $(document).height() / 100) {
    $("#spopup").show("slow");
    $(window).off('scroll');
  } else {
    $("#spopup").hide("slow");
  }
});

function closeSPopup() {
  $('#spopup').hide('slow');
}

worked for me