Use rollup to bundle.

Sortable.js

@@ -5,26 +5,12 @@
  * @license MIT
  */
 
-(function sortableModule(factory) {
-	"use strict";
+"use strict";
 
-	if (typeof define === "function" && define.amd) {
-		define(factory);
-	}
-	else if (typeof module != "undefined" && typeof module.exports != "undefined") {
-		module.exports = factory();
-	}
-	else {
-		/* jshint sub:true */
-		window["Sortable"] = factory();
-	}
-})(function sortableFactory() {
-	"use strict";
+import { version } from './package.json';
 
 	if (typeof window === "undefined" || !window.document) {
-		return function sortableError() {
-			throw new Error("Sortable.js requires a window with a document");
-		};
+		throw new Error("Sortable.js requires a window with a document");
 	}
 
 	var dragEl,
@@ -2455,6 +2441,6 @@
 
 
 	// Export
-	Sortable.version = '1.9.0';
-	return Sortable;
-});
+	Sortable.version = version;
+
+	export default Sortable;

index-es.js

@@ -0,0 +1,7 @@
+import Sortable from './Sortable';
+
+export default Sortable;
+
+export {
+    Sortable
+}

index-iife.js

@@ -0,0 +1,3 @@
+import Sortable from './Sortable';
+
+export default Sortable;

index.html

@@ -365,7 +365,7 @@ <h3 class="col-6"><a target="_blank" href="https://github.com/SortableJS/polymer
 
 
 	<!-- Latest Sortable -->
-	<script src="./Sortable.js"></script>
+	<script src="dist/sortable.js"></script>
 
 	<script type="text/javascript" src="st/prettify/prettify.js"></script>
 	<script type="text/javascript" src="st/prettify/run_prettify.js"></script>

package.json

@@ -3,18 +3,17 @@
 	"exportName": "Sortable",
 	"version": "1.9.0",
 	"devDependencies": {
-		"gulp": "^4.0.0",
-		"gulp-each": "^0.5.0",
-		"gulp-rename": "^1.4.0",
-		"gulp-uglify": "^3.0.1",
-		"http-server": "^0.9.0",
-		"pump": "^3.0.0"
+		"rollup": "^1.10.1",
+		"uglify-js": "^3.5.5"
 	},
 	"description": "JavaScript library for reorderable drag-and-drop lists on modern browsers and touch devices. No jQuery required. Supports Meteor, AngularJS, React, Polymer, Vue, Knockout and any CSS library, e.g. Bootstrap.",
 	"main": "Sortable.js",
+	"module": "index-es.js",
 	"scripts": {
-		"http-server": "http-server -s ./",
-		"prepublish": "gulp build"
+		"prepublish": "npm run build",
+		"build": "rollup -c rollup.config.js && npm run min",
+		"min": "uglifyjs -mangle --comments=/@license/ -o dist/sortable.min.js -- dist/sortable.js",
+		"watch": "npm run build -- --watch"
 	},
 	"maintainers": [
 		"Konstantin Lebedev <ibnRubaXa@gmail.com>",

rollup.config.js

@@ -0,0 +1,13 @@
+import json from 'rollup-plugin-json';
+
+export default [
+  {
+    input: 'index-iife.js',
+    output: {
+      file: 'dist/sortable.js',
+      format: 'iife',
+      name: 'Sortable'
+    },
+    plugins: [json()]
+  }
+];