ShadowRealm API Polyfill

A implementation of the ShadowRealm API Proposal, a JavaScript sandbox, test with TC39 Test262 cases.

简体中文 | English

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

Try it now 🎉

Install

npm i -S shadowrealm-api

Usage

Ponyfill: non-invasive

import ShadowRealm from 'shadowrealm-api'

const realm = new ShadowRealm();

Polyfill: patch up the global object

import 'shadowrealm-api/browser/polyfill.mjs'

const realm = new ShadowRealm();

Debugging

Print internal info for debugging

ShadowRealm.__debug = true;

Limitations

1. All code evaluated inside a ShadowRealm runs in strict mode;
2. The ESM statement must not contain redundant comments;

// ❌
import/* */defaultExport from "module-name";
export default/* */'xxx';

// ✅
import defaultExport from "module-name";
export default 'xxx';

3. Exporting variable declarations is not supported;

// ❌
export const obj = {...}, fn = () => {...};

// ✅
const obj = {...}, fn = () => {...};
export { obj, fn };

Compatibility

Notes:

1. Don't support destructuring assignment in ESM statement;
2. Need Promise polyfill in ShadowRealm;
3. Need fetch polyfill in top window;
4. Need URL polyfill in top window;

Use fetch or URL polyfill:

import "fetch polyfill";
import "URL polyfill";
import "shadowrealm-api/browser/polyfill.mjs";
// Your codes

Use Promise polyfill:

ShadowRealm.__shims = [
    'path/to/promise-polyfill.js',
    'other polyfills',
];

Contact

1. WeChat: cai_fanwei
2. QQ Group: 663286147
3. E-mail: [email protected]