scroll_trigger.js

var scrolledElement = $('#headerToScroll').offset().top;
var fomoTriggered = false;
var windowScroll = function() { 
  $(window).on('scroll', function(){
    var y_scroll_pos = window.pageYOffset;
    var scroll_pos_test = scrolledElement;

    if(y_scroll_pos > scroll_pos_test){
      console.log('scroll event triggered');
      if (!fomoTriggered){
        fomoTriggered = true;
        fomo.trigger('start');
      }
    }
  });
}

var loadScript = function(location, callback){
  var fileRef = document.createElement('script');
  fileRef.setAttribute('type','text/javascript');

  if (callback) {
    if (fileRef.readyState) {  // IE
      fileRef.onreadystatechange = function() {
        if (fileRef.readyState == 'loaded' || fileRef.readyState == 'complete') {
          fileRef.onreadystatechange = null;
          callback();
        }
      };
    } else {  // Non-IE
      fileRef.onload = function(){
        callback();
      };
    }
  }

  fileRef.setAttribute('src', location);
  document.head.appendChild(fileRef);
};

loadScript("https://load.fomo.com/api/v1/XXXXXXXX/load.js", windowScroll);