• Stage 1

• @dherman
• @caridy
• @erights

You can view the spec rendered as HTML.

• worked on this during ES2015 time frame, so never went through stages process
• got punted to later (rightly so!)
• goal of this proposal: resume work on this, reassert committee interest via advancing to stage 1
• original idea from @dherman: What are Realms?

• sandbox
• iframe without DOM
• principled version of Node's 'vm' module
• sync Worker

• security isolation (with synchronous but coarse-grained communication channel)
• plugins (e.g., spreadsheet functions)
• in-browser code editors
• server-side rendering
• testing/mocking (e.g., jsdom)
• in-browser transpilation

let realm = new Realm();

let outerGlobal = window;
let innerGlobal = realm.global;

let f = realm.evalScript("(function() { return 17 })");

f() === 17 // true

Reflect.getPrototypeOf(f) === outerGlobal.Function.prototype // false
Reflect.getPrototypeOf(f) === innerGlobal.Function.prototype // true

class EmptyRealm extends Realm {
  constructor(...args) { super(...args); }
  init() { /* do nothing */ }
}

class FakeWindow extends Realm {
  init() {
    super.init(); // install the standard primordials
    let global = this.global;

    global.document = new FakeDocument(...);
    global.alert = new Proxy(fakeAlert, { ... });
    ...
  }
}

class ESNextRealm extends Realm {
  [Realm.directEval](source) { return compile(source); }
  [Realm.indirectEval](source) { ... }
  ...
}

• https://gist.github.com/dherman/9146568

A shim implementation of the Realm API can be found here.

And you can play around with the Shim here.

The source for the spec text is located in spec/index.emu and it is written in ecmarkup language.

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

npm install
npm run build
open index.html

Alternative, you can use npm run watch.