sticky.js

class Sticky {
  constructor() {
    console.log('>>> Sticky constructor');

    const that = this;
    let scrollTop = $(window).scrollTop();

    $('.js-sticky').each(function() {
      let el = $(this),
          offset = el.data('offset') || $(window).height() - 100;

      that.stickyElement(scrollTop, el, offset);

      $(window).scroll(function() {
        scrollTop = $(window).scrollTop();
        that.stickyElement(scrollTop, el, offset);
      });
    });
  }

  stickyElement(scrollTop, element, offset) {
    if (scrollTop >= offset) {
      element.addClass('-sticky');
    } else {
      element.removeClass('-sticky');
    }
  }
}

export default Sticky;