docs: function destroy() {
          ScrollSpy._elements.splice(ScrollSpy._elements.indexOf(this), 1);
          ScrollSpy._elementsInView.splice(ScrollSpy._elementsInView.indexOf(this), 1);
          ScrollSpy._visibleElements.splice(ScrollSpy._visibleElements.indexOf(this.$el), 1);
          ScrollSpy._count--;
          this._removeEventHandlers();
          $(this.options.getActiveElement(this.$el.attr('id'))).removeClass(this.options.activeClass);
          this.el.M_ScrollSpy = undefined;
        }