parallel

!logo

execute an async transform and yield in order of completion

[![NPM version][npm-image]][npm-url]
[![Travis Status][travis-image]][travis-url]
[![Travis Status][codecov-image]][codecov-url]

Usage

_package requires a system that supports async-iteration, either natively or via down-compiling_

$3

``
npm install @async-generators/parallel --save
yarn add @async-generators/parallel
`

This package's main entry points to a commonjs distribution.

Additionally, the module entry points to a es2015 distribution, which can be used by build systems, such as webpack, to directly use es2015 modules.

Api

$3

parallel() iterates source and executes selector(item, index) concurrently. Upon resolution of selector promise, the result is yielded.

selector(item) is awaited in a non-blocking fashion and parallel results are yielded in the _order of completion_.

If the the number of concurrent tasks is greater-than or equal-to limit further iteration of source is halted until other tasks complete. Upon halting, the limited(item, index) method is called (sync). If limited returns true the item is ignored not _not_ passed to selector

source must have a [Symbol.asyncIterator] or [Symbol.iterator] property. If both are present only [Symbol.asyncIterator] is used.

$3

parallel() iterates source and awaits each item concurrently. Upon resolve, the result is yielded. source items are awaited in a non-blocking fashion and the results are yielded in the _order of completion_.

source must have a [Symbol.asyncIterator] or [Symbol.iterator] property. If both are present only [Symbol.asyncIterator] is used. source should _ideally_ yield executing promises, but technically can yield an object - although this makes the call to parallel entirely redundant.

Example

example.js
`js
const parallel = require('@async-generators/parallel').default;

async function* source() {
yield 1; yield 2; yield 3; yield 4;
}

function delay(item) {
let duration = {
1: 500,
2: 200,
3: 1000,
4: 700
}
return new Promise(r => setTimeout(r, duration[item ]));
}

async function main() {
for await (let item of
parallel(source(), async (value) => {
await delay(value);
return value;
})
) {
console.log(item);
}
}

main();

`

Execute with the latest node.js:

`
node --harmony-async-iteration example.js
`


output:
`
2
1
4
3
`


Typescript

This library is fully typed and can be imported using:

`ts
import parallel from '@async-generators/parallel');
`

It is also possible to directly execute your properly configured typescript with ts-node:

`
ts-node --harmony_async_iteration example.ts
``

[npm-url]: https://npmjs.org/package/@async-generators/parallel
[npm-image]: https://img.shields.io/npm/v/@async-generators/parallel.svg
[npm-downloads]: https://img.shields.io/npm/dm/@async-generators/parallel.svg
[travis-url]: https://travis-ci.org/async-generators/parallel
[travis-image]: https://img.shields.io/travis/async-generators/parallel/master.svg
[codecov-url]: https://codecov.io/gh/async-generators/parallel
[codecov-image]: https://codecov.io/gh/async-generators/parallel/branch/master/graph/badge.svg