ShadowRealm S2.7

Proposal details

Stage: Stage 2.7
Status: Active
ECMAScript edition: —
Synchronized: Aug 28, 2026
中文译文 · Source repository

Proposal overview

The ShadowRealm proposal addresses the need for creating isolated JavaScript environments by providing a standard API to create a distinct global environment with its own intrinsics and built-ins. It provides a class with methods to evaluate source text synchronously and dynamically import modules asynchronously, returning only primitive values or callable functions.7, the proposal has evolved from an earlier globalThis-based model to a leaner, isolated realm API.

Note

The README below comes from the upstream repository and may contain outdated stage or status metadata. Use the proposal details above as the current source of truth.

ECMAScript spec proposal for ShadowRealm API

Status

Champions

@dherman
@caridy
@erights
@leobalter
@rwaldron
@legendecas

Index

What are ShadowRealms?
API (TypeScript Format)
Presentations
History
Contributing
- Updating the spec text for this proposal

What are ShadowRealms?

ShadowRealms are a distinct global environment, with its own global object containing its own intrinsics and built-ins (standard objects that are not bound to global variables, like the initial value of Object.prototype).

See more at the explainer document.

API (TypeScript Format)

declare class ShadowRealm {
    constructor();
    importValue(specifier: string, bindingName: string): Promise<PrimitiveValueOrCallable>;
    evaluate(sourceText: string): PrimitiveValueOrCallable;
}

See some examples in the Explainer file.

Presentations

History

we moved on from the exposed globalThis model to a lean isolated realms API (see https://github.com/tc39/proposal-shadowrealm/issues/289 and https://github.com/tc39/proposal-shadowrealm/issues/291)
we worked on this during ES2015 time frame, so never went through stages process (ES6 Realm Objects proto-spec.pdf)
got punted to later (rightly so!)
original idea from @dherman: What are Realms?

Contributing

Updating the spec text for this proposal

The source for the spec text is located in spec.html and it is written in ecmarkup language.

When modifying the spec text, you should be able to build the HTML version by using the following command:

npm install
npm run build
open dist/index.html

Alternatively, you can use npm run watch.

#ShadowRealm S2.7

#ECMAScript spec proposal for ShadowRealm API

#Status

#Champions

#Index

#What are ShadowRealms?

#API (TypeScript Format)

#Presentations

#History

#Contributing

#Updating the spec text for this proposal