jQuery Loader for Slideshow on Large Screens, Single Image on Small Screens

gistfile1.js

// jQuery script to pull images and load bxslider slideshow for large screen, load single image (no slideshow) for small screens and old IE
// Tested on Chrome, FF, IE11, iOS, Surface

function slideshow_loader() {
  var dir = "slideshow/";
  var large_width = "780";
  var small_width = "530";
  var $img;
  
  if ($(window).width() > 568) {
	// hide slideshow from older versions of IE  
	if (!$('html').hasClass('ie')) {
		$.ajax({
			//This will retrieve the contents of the folder if the folder is configured as 'browsable'
			url: dir,
			success: function (data) {
				// sort through each jpg in directory
				$(data).find('a').each(function () {
					if ($(this).attr('href').match(/(jpg)$/i) !== null) {
						var filename = this.href.split('/').pop();
						if ($(window).width() > 840) { 
							//load larger photos for large screens
							if (filename.indexOf(small_width) === -1) {
							  $img = $("<img>", {src: "slideshow/" + filename});
							  $img.appendTo("#bxslider");
							  $img.wrap("<li></li>");
							}
						} else {
						   //smaller photos for small <840 screens
						   if (filename.indexOf(large_width) === -1) {
								$img = $("<img>", {src: "slideshow/" + filename});
								$img.appendTo("#bxslider");
								$img.wrap("<li></li>");
						   }
						}
					}
				});
				$('#bxslider').bxSlider({
				  auto: true,
				  autoControls: true,
				  mode: 'fade',
				  captions: true,
				  pause: 5000,
				  speed: 1200,
				  preloadImages: 'all'
				});
			}
			
		});
	  } else {
		  // older versions of IE get a static image
		  $img = $("<img>", {src: "slideshow/slide1_" + large_width + ".jpg"});
		  $img.appendTo("#bxslider");
		  $img.wrap("<li class='slide_photo'></li>");
	  }
  } else {
	// static image for the smallest mobile devices to save bandwidth  
	$img = $("<img>", {src: "slideshow/slide1_" + small_width + ".jpg"});
	$img.appendTo("#bxslider");
	$img.wrap("<li class='slide_photo'></li>");
  }
}