Prevent scrolling of parent element.

prevent_parent_scroll.js

jQuery($ =>
  $(document).on('wheel', '.scrollable', function(ev) {
    let $el = $(this);
    let height = $el.outerHeight(true);
    let delta = ev.originalEvent.deltaY;
    let up = delta < 0;

    let prevent = function() {
      ev.stopPropagation();
      ev.preventDefault();
      ev.returnValue = false;
      return false;
    };

    if (!up && (delta > (this.scrollHeight - height - this.scrollTop))) {
      // Scrolling down, but this will take us past the bottom.
      $el.scrollTop(this.scrollHeight);
      return prevent();
    } else if (up && (-delta > this.scrollTop)) {
      // Scrolling up, but this will take us past the top.
      $el.scrollTop(0);
      return prevent();
    }
  })
);