$(document).ready(function() {
  var sectionIds = $('a.nav-link');
  $(document).scroll(function() {
    sectionIds.each(function() {
      var container = $(this).attr('href');
      var containerOffset = $(container).offset().top;
      var containerHeight = $(container).outerHeight();
      var containerBottom = containerOffset + containerHeight;
      var scrollPosition = $(document).scrollTop();
      if (scrollPosition < containerBottom - 350 && scrollPosition >= containerOffset - 350) {
        $(this).addClass('active');
      } else {
        $(this).removeClass('active');
      }
    });
  });
});