gsathya

// Based on https://web.archive.org/web/20160310120458/http://wiki.ecmascript.org/doku.php?id=strawman:scoped_object_extensions

// in whatever-extras.js
import Whatever from './whatever.js';

export extension Extensions = Whatever.protoype {
  somethingComplex: function() { ... }
}

// in user code

gsathya

Object.defineProperty(Number.prototype,Symbol.iterator,{
  *value({ start = 0, step = 1 } = {}) {
     var inc = this > 0 ? step : -step;
     for (let i = start; Math.abs(i) <= Math.abs(this); i += inc) {
        yield i;
     }
  },
  enumerable: false,
  writable: true,
  configurable: true

gsathya

➜  v8 git:(69191fe7d6) eshost -t _test.js
┌────────────────┬───────────┐
│ chakra         │ 4         │
├────────────────┼───────────┤
│ javascriptcore │ 4         │
├────────────────┼───────────┤
│ spidermonkey   │ 4         │
├────────────────┼───────────┤
│ v8             │ undefined │
├────────────────┼───────────┤