The Interactive Extensions for JavaScript
JavaScript TypeScript
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The Interactive Extensions for JavaScript (IxJS)...

...is a set of libraries to compose synchronous and asynchronous collections and Array#extras style composition in JavaScript

The Interactive Extensions for JavaScript (IxJS) is a library for creating and composing asynchronous sequences using both the Iterable and AsyncIterable classes.

Iterable

The Iterable class a way to create and compose synchronous collections much like Arrays, Maps and Sets in JavaScript using the Array#extras style using the familiar methods you are used to like map, filter, reduce and more.

const Iterator = require('ix').Iterator;

Iterator.from([1,2,3,4])
  .filter(x => x % 2 === 0)
  .map(x => x * 2)
  .forEach(x => console.log(`Next ${x}`));

// => 4
// => 8

The Iterable class implements the iterator pattern in JavaScript by exposing the [Symbol.iterator] method which in turn exposes the Iterator class. The iterator yields values by calling the next() method which returns the IteratorResult class.

interface Iterable<T> {
  [Symbol.iterator](): Iterator<T>;
}

interface Iterator<T> {
  [Symbol.iterator](): Iterator<T>;
  next(): IteratorResult<T>;
}

interface IteratorResult<T> {
  value: T;
  done: Boolean;
}

AsyncIterable

The AsyncIterator class is based off the ECMAScript Proposal for Asynchronous Iterators. This would allow us to create asynchronous collections of Promises and be able to use such methods as the map, filter, reduce and other Array#extras methods that you are used to using.

const AsyncIterable = require('ix').AsyncIterable;

async function *gen() {
  yield Promise.resolve(1);
  yield Promise.resolve(2);
  yield Promise.resolve(3);
  yield Promise.resolve(4);
}

AsyncIterable.from(gen())
  .filter(x => x % 2 === 0)
  .map(x => x * 2)
  .forEachAsync(x => console.log(`Next ${x}`))
  .catch(err => console.log(`Error ${err}`));

// => 4
// => 8

The AsyncIterable class implements the async iterator pattern in JavaScript by exposing the [Symbol.asyncIterator] method which in turn exposes the AsyncIterator class. The iterator yields values by calling the next() method which returns a Promise which resolves a IteratorResult class.

interface AsyncIterable<T> {
  [Symbol.asyncIterator](): AsyncIterator<T>;
}

interface Iterator<T> {
  [Symbol.asyncIterator](): Iterator<T>;
  next(value): Promise<IteratorResult<T>>;
  [optional] throw(value): Promise<IteratorResult<T>>;
  [optional] return(value): Promise<IteratorResult<T>>;
}

interface IteratorResult<T> {
  value: T;
  done: Boolean;
}

License

The MIT License (MIT)

Copyright (c) ReactiveX

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.