If you want a reference to the global object that works in any context, you can read this from a directly-called function. const global = (function() {return this})();. This evaluates to window in the browser, self in a service worker and global in nodejs.

Universal = code that can run in any JS runtime (browser and/or node). Isomorphic = application that runs the same universal code in multiple runtimes to avoid code duplication.

Remember that "JavaScript" does not mean that the DOM API, AJAX, HTML5 <canvas> (and so on) are available - it just means the JavaScript scripting language is being used - that's it.

Ubiquity: you can also run your validation on the server side (e.g. nodejs)

use universal loading to render identical HTML on both the server and client.

The “shared” schema is effectively the API schema. These are the fields exchanged in the API, common to client and server.

React is an isomorphic/universal framework. That means that there is a virtual representation of the UI component tree, and that is separate from the actual rendering that it outputs in the browser.

zxcvbn works identically on the server

The “universal” label that has been slapped on to it is superfluous, but it does have its merits. Now that we have a commonly known term to refer to environment agnostic JavaScript code, it allows library authors to list it as a feature and be fashionable doing it. I’m happy with the term “universal” being fashionable because it makes developers think about their dependencies on the runtime environment. In the end this will help the JavaScript ecosystem mature and allow libraries to be used everywhere.

The “universal” label that has been slapped on to it is superfluous

Running the same code in the browser and on the server in order to avoid code duplication is a very different problem. It is simply a matter of good development practices to avoid code duplication. This however is not limited to isomorphic applications. A utility library such as Lodash is “universal”, but has nothing to do with isomorphism. Sharing code between environments does not give you an isomorphic application. What we’re referring to with Universal JavaScript is simply the fact that it is JavaScript code which is environment agnostic. It can run anywhere. In fact most JavaScript code will run fine on any JavaScript platform.

Maybe we should distinguish between: The technique of asssembling pages on either client or server. Here, “isomorphic” and “full stack” (as proposed by Rodrigo Medeiros) seem good choices. JavaScript that runs in all (or most) JavaScript environments, especially browsers and Node.js. Here, “universal” seems a good choice.