function bootstrapTabControl(){
  const items = $('.nav-link');
  const pane = $('.tab-pane');
  const itemsLength = items.length;

  // next
  $('.nexttab').on('click', () => {
      let activeIndex;
      for(let i = 0; i < itemsLength; i++){
          if(items.eq(i).hasClass('active')){
              activeIndex = i;
              break;
          }
      }
      if(activeIndex < itemsLength - 1){
          // for tab
          items.eq(activeIndex).removeClass('active');
          items.eq(activeIndex + 1).addClass('active');
          // for pane
          pane.eq(activeIndex).removeClass('show active');
          pane.eq(activeIndex + 1).addClass('show active');
      }
      location.hash = items.eq(activeIndex + 1).attr("href");
  });

  // Prev
  $('.prevtab').on('click', () => {
      let activeIndex;
      for(let i = 0; i < itemsLength; i++){
          if(items.eq(i).hasClass('active')){
              activeIndex = i;
              break;
          }
      }
      if(activeIndex !== 0){
          // for tab
          items.eq(activeIndex).removeClass('active');
          items.eq(activeIndex - 1).addClass('active');
          // for pane
          pane.eq(activeIndex).removeClass('show active');
          pane.eq(activeIndex - 1).addClass('show active');
      }
      location.hash = items.eq(activeIndex - 1).attr("href");
  });
}
bootstrapTabControl();

const topFunction = () => {
  document.body.scrollTop = 0; // For Safari
  document.documentElement.scrollTop = 0; // For Chrome, Firefox, IE and Opera
}

topFunction();