jquery

scroll-offset-event.js

$(document).on('scroll', function(e) {
  var $documentHeight = $(this).height();
  var $currentScrollOffset = $(this).scrollTop() + $(window).height(); // Scroll Top + the current window height
  var distanceToBottom = $documentHeight - $currentScrollOffset;
  var offsetEventTrigger = 100;

  console.log('$documentHeight', $documentHeight);
  console.log('$currentScrollOffset', $currentScrollOffset);
  console.log('Distance to bottom of document : ', distanceToBottom);

  if(distanceToBottom < offsetEventTrigger) {
    // do your logic here
    console.log('Trigger your event call api endpoint');
  }

})