# @async-generators/terminator

> inform an iterator when it is prematurely terminated by the consumer.

Latest version **0.4.0** (published 2018-01-16) · MIT license · 0 weekly downloads

## Install

```sh
npm install @async-generators/terminator
pnpm add @async-generators/terminator
yarn add @async-generators/terminator
bun add @async-generators/terminator
```

## Health

**Score 30/100 (F)** — status: abandoned.

Positive: has types; esm support; no vulnerabilities; high quality score.

Warnings: low downloads; pre 1.0.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 0.4.0 |
| Published | 2018-01-16 |
| First published | 2017-09-26 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | bundled |
| Module format | ESM + CommonJS |
| Node | >=9.0.0 |
| Dependencies | 0 |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 0 |
| Author | Meirion Hughes |
| Maintainers | meirionhughes |
| Keywords | async, iterator, generator, esnext, typescript, linq |

## Links

- npm: https://www.npmjs.com/package/@async-generators/terminator
- Repository: https://github.com/async-generators/terminator
- Homepage: https://github.com/async-generators/terminator#readme
- Issues: https://github.com/async-generators/terminator/issues
- npm.io page: https://npm.io/package/@async-generators/terminator

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## Recent versions

- 0.4.0 (latest) — 2018-01-16
- 0.3.1 — 2018-01-12
- 0.3.0 — 2018-01-12
- 0.2.0 — 2017-09-26
- 0.1.1 — 2017-09-26
- 0.1.0 — 2017-09-26

## README

# terminator
[![logo](https://avatars1.githubusercontent.com/u/31987273?v=4&s=110)][async-url]

inform an iterable when it is prematurely terminated by the consumer. 

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

### Install
```
yarn add @async-generators/terminator
```

This package's `main` entry points to a `commonjs` dist. 
The `module` entry points to a `es2015` module dist. Both require require native async-generator support, or be down-compiled with a webpack loader. 

## Api

### terminator(source)

<code>terminator()</code> returns an iterable that, when iterated, wraps the source iterable and captures calls to `return`. When a compliant consumer (`for`, `for-await`) terminates iteration, then the `return` call is rerouted to call `next(Symbol.for("terminated"))`. The original `source` iterable can then find out if it was terminated by examining the return value of `yield` to see if it equals `Symbol.for("terminated")`;

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

## Example

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

async function* source() {
  for (let i = 0; i < 10; i++) {
    let terminated = (yield i) == Symbol.for("terminated");
    if (terminated) {
      console.log("clean-up on aisle five!");
      return;
    }
  }
}

async function main(){
  for await (let item of terminator(source())){
    if(item > 4){
      break;
    }
    console.log(item);
  }
}

main().catch(console.log);
```

Execute with the latest node.js: 

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

output:
```
0
1
2
3
4
clean-up on aisle five!
```
## Typescript

This library is fully typed and can be imported using: 

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

It is also possible to directly execute your [properly configured](https://stackoverflow.com/a/43694282/1657476) typescript with [ts-node](https://www.npmjs.com/package/ts-node):

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

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

---
_Source: https://npm.io/package/@async-generators/terminator · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._