Iterator helpers polyfill
A polyfill for the ECMAScript proposal “Iterator Helpers” (documentation for this proposal).
Warning
Don’t trust this code:
- It’s mostly untested.
- I cut corners to make the TypeScript types work.
Caveats:
- The focus is on simple code, not on spec compliance.
- I use textual search-and-replace to convert the asynchronous code to synchronous code.
- Performed via:
npm run syncify
- Performed via:
Functionality:
- This polyfill implements all constructs specified in the proposal.
- This polyfill deliberately does not provide any additional functionality.
Installation
npm install @rauschma/iterator-helpers-polyfillExamples
Polyfill
import assert from 'node:assert/strict';
import '@rauschma/iterator-helpers-polyfill/install'; // install polyfill globally
assert.deepEqual(
new Set(['a', 'b', 'c']).values()
.map(x => x + x).toArray(),
['aa', 'bb', 'cc']
);
assert.deepEqual(
new Set(['a', 'b', 'c']).values()
.filter(x => x <= 'b').toArray(),
['a', 'b']
);
assert.deepEqual(
new Set(['a', 'b', 'c']).values()
.take(1).toArray(),
['a']
);Library (doesn’t change JavaScript’s globals)
import assert from 'node:assert/strict';
import {XIterator} from '@rauschma/iterator-helpers-polyfill';
assert.deepEqual(
XIterator.from(new Set(['a', 'b', 'c']))
.map(x => x + x).toArray(),
['aa', 'bb', 'cc']
);
assert.deepEqual(
XIterator.from(new Set(['a', 'b', 'c']))
.filter(x => x <= 'b').toArray(),
['a', 'b']
);
assert.deepEqual(
XIterator.from(new Set(['a', 'b', 'c']))
.take(1).toArray(),
['a']
);More examples
Material on iterator helpers
- ECMAScript proposal “Iterator Helpers”: https://github.com/tc39/proposal-iterator-helpers
- Blog post: https://2ality.com/2022/12/iterator-helpers.html