Robot439

$('.parent').bind('touchmove',function(e) {
  e.preventDefault();
  var touch = e.originalEvent.touches[0] || e.originalEvent.changedTouches[0];
  var position = $(this).offset();
  var maxWidth = $(this).width();
  var x = touch.pageX - position.left;
  if (0 <= x && x <= maxWidth) $(".modal").width(x);
});