locale-extensions VS proposal-shadowrealm

Locale Extensions:Allow Web platform engines to use limited system-defined user preferences.

ShadowRealm: ECMAScript Proposal, specs, and reference implementation for Realms [Stage 3 -> 2].

You can't out of the box. There is an open issue on the Node.js repositoryto let the node:vm module to use the vm's context, but it is still open. It seems that the Node.js core team is interested in fixing this problem by implementing the new ShadowRealm spec, and I think we will make some progress during 2023.

ShadowRealms — a successor of the Realms proposals, this API is intended for use cases exactly like plugins or extension systems, providing an option for creating distinct global environments to run the code in. While not entirely secure on its own, this API could provide a strong foundation to build actual extension systems on the Web. That said, 4 years later, the TC39 proposal is currently only at stage 3, not implemented by any browser;

With --no-isolate it was 2.8x faster than vitest and 1.7x faster than Jest, but 19 tests failed (see table above). Some people report issues with watch mode when using --no-isolate. So I decided to not pursue it any further. Once the vm module that Vitest relies on supports ESM, or when the amazingly named Shadow Realms are added to JavaScript, we will likely get this performance boost for free without the downsides.

If ShadowRealms are ever added to EcmaScript (and implemented into V8/Node) they'll allow for a different approach to isolating code that would be faster without the downsides of sharing global.

Eventually I will get around to creating a "proper" package by just grabbing all the JS that is loaded by the code in the iframe, and bundling it up. We really need the ShadowRealm proposal to go through because the perchance engine messes with a lot of JS internals, so it would mess up the rest of your app. Could do it in a WebWorker, but then everything would have to be async.

The upcoming JavaScript Shadow Realms proposal looks like it solves a similar problem: https://github.com/tc39/proposal-shadowrealm/blob/main/expla...

Browser-based JavaScript doesn't yet have a way to isolate code fully in this manner though there is a new JavaScript feature on the way that would provide this capability. Its called ShadowRealm and would basically give you a new global context to execute code that's completely separate from your main document code.