function addSwipeListener(el, listener) {
  var startX;
  var dx;
  var direction;
 
  function cancelTouch() {
    el.removeEventListener('touchmove', onTouchMove);
    el.removeEventListener('touchend', onTouchEnd);
    startX = null;
    startY = null;
    direction = null;
    dx = 0;
  }
 
  function onTouchMove(e) {
    if (e.touches.length > 1) {
      cancelTouch();
    } else {
      dx = e.touches[0].pageX - startX;
      var dy = e.touches[0].pageY - startY;
      if (direction == null) {
        direction = dx;
        e.preventDefault();
      } else if ((direction < 0 && dx > 0) || (direction > 0 && dx < 0) || Math.abs(dy) > 15) {
        cancelTouch();
      }
    }
  }

  function onTouchEnd(e) {
    cancelTouch();
    if (Math.abs(dx) > 50) {
      listener({ target: el, direction: dx > 0 ? 'right' : 'left', dx: dx });
    }
  }
 
  function onTouchStart(e) {
    if (e.touches.length == 1) {
      startX = e.touches[0].pageX;
      startY = e.touches[0].pageY;
      el.addEventListener('touchmove', onTouchMove, false);
      el.addEventListener('touchend', onTouchEnd, false);
    }
  }
 
  el.addEventListener('touchstart', onTouchStart, false);
}