use babel

.jshintrc

     "newcap": true, // true: Require capitalization of all constructor functions e.g. `new F()`
     "maxlen": 80, // {int} Max number of characters per line
     "latedef": false, //This option prohibits the use of a variable before it was defined
-    "laxbreak": true //Ignore line breaks around "=", "==", "&&", etc.
+    "laxbreak": true, //Ignore line breaks around "=", "==", "&&", etc.
+    "esnext": true //support ES2015
 }

app.js

 /* global $, JitsiMeetJS, config, Promise */
 /* application specific logic */
 
+import "babel-polyfill";
 require("jquery");
 require("jquery-ui");
 require("strophe");

package.json

     "jshint": "2.8.0",
     "precommit-hook": "3.0.0",
     "uglify-js": "2.4.24",
-    "clean-css": "*"
+    "clean-css": "*",
+    "babelify": "*",
+    "babel-preset-es2015": "*",
+    "babel-polyfill": "*"
   },
   "license": "Apache-2.0",
   "scripts": {
   ],
   "browserify": {
     "transform": [
-      "browserify-shim"
+      "browserify-shim",
+      ["babelify", {
+        "ignore": "node_modules"
+      }]
     ]
   },
+  "babel": {
+    "presets": ["es2015"]
+  },
   "browser": {
     "jquery": "./node_modules/jquery/dist/jquery.js",
     "jquery-ui": "./node_modules/jquery-ui/jquery-ui.js",