// Reference: https://www.delftstack.com/howto/javascript/detect-finger-swipe-events-in-javascript/

window.addEventListener('load', () => {
  document.body.addEventListener('touchstart', onTouchStart);
  document.body.addEventListener('touchmove', onTouchMove);
  document.body.addEventListener('touchend', onTouchEnd);
})

var startX, startY, moveX, moveY;

function onTouchStart(e){
  startX = e.touches[0].clientX;
  startY = e.touches[0].clientY;
}

function onTouchMove(e){
  moveX = e.touches[0].clientX;
  moveY = e.touches[0].clientY;
}

function onTouchEnd(){
  if (startY+100 < moveY){
    goToPreviousSlide();
  } else if (startY-100 > moveY){
    goToNextSlide();
  }
}