There's tons! These are the most common and easiest: You can simply run a localhost server with a simple tool like http-server . No internet connection required since it's all local to your machine. You can bundle your code with a bundler like Webpack, Rollup, etc which would then transform all of your files into one which you can easily use in any browser. More on reddit.com

It’s basically a transition moment right now. The import/export syntax didn’t exist on the front-end when Node made the require syntax. Once import/export was added as a language feature, Node began to support it but not all existing modules have been updated. In fact, most probably haven’t as import/export is a relatively new feature. So, my advice would be to stick with require for the time being but plan to switch eventually. (I’m personally probably going to wait a year or so. When I do decide to switch, I’m going to test each module one-by-one and see which ones have or haven’t been updated. If it’s been that long without an update, it might be time to look for an alternative anyway.) More on reddit.com

You get it right - you have to add use strict in cjs More on reddit.com

Is it wrong or not correct to use IIFE in ecma modules? It's not exactly "wrong". You can put IIFE's wherever you want. That's up to you. But it certainly isn't necessary. IIFE's biggest benefits comes in that they let you write code that doesn't pollute global with your variables. But they've been outdated since ES6 with block level scoping and modules. With modules you have a completely new, independent, non-global scope that you're variables are getting defined in. There's no need to worry about them being added to global. Effectively, a module is the same as the inside of an IIFE. If you're in a module and want to expose a function called getString, simply define that function and export it by name. function getString() { return "hi there!"; } export { getString } You can even export it as part of the declaration export function getString() { return "hi there!"; } No IIFE is necessary. No wrapper object is necessary (the {} in the first export isn't really an object, just a container for your exported names). When someone wants to import your function they can do it by name import { getString } from "js/file.js"; Or if they want an object (a Module object) with that function inside it, they can use import * as myModule from "js/file.js"; // use myModule.getString() More on reddit.com