Reuse multiple existing IIFEs in react app

I have IIFE functions for some of the library code in an legacy application that needs to work for IE10+ (No ES6 module loading, etc).

However, I am starting to develop an React app that will be using ES6 and TypeScript and I want to reuse the code I already have without duplicating the files. After a bit of research I found that I’d want to use a UMD pattern to allow these library files to work both as <script src=*> imports and to allow the React app to import them via ES6 module loading.

I came up with the following conversion:

var Utils = (function(){
  var self = {
    MyFunction: function(){
  return self;


(function (global, factory) {
    typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
    typeof define === 'function' && define.amd ? define(['exports'], factory) :
    (factory((global.Utils = {})));
}(this, (function (exports) { 
  exports.MyFunction = function(){

This will allow loading via Import Utils from './Utils.js' command and also allow it to be inserted using a script tag <script src='Utils.js'></script>

However, some of my IIFE use other IIFE’s as a dependency (bad I know but a reality).

var Utils = Utils; // Used to indicate that there is dependency on Utils
var RandomHelper = (function(){
  var self = {
    DoThing: function(){
  return self;

If correctly turn RandomHelper and Utils into files that can be imported, the React app isn’t compatible with this technique. Doing simply

Import Utils from './Utils.js'
Import RandomHelper from './RandomHelper.js'

does not work because I believe Utils is not window scoped. It will load without issue but RandomHelper.DoThing() will throw that Utils is not defined.

In the legacy app

<script src='Utils.js'></script>
<script src='RandomHelper.js'></script>

works flawlessly.

How can I have RandomHelper be able to use Utils in a React app, keeping it IE and ES5 compatible but still work in react. Perhaps somehow setting a window/global variable?

PS: I understand the point of the ES6 module loading is to deal with dependencies and my existing IIFEs are not ideal. I plan to eventually switch es6 classes and better dependency control but for now I want to use whats available to be without re-writing

Source: ReactJs