122 lines
5.1 KiB
Markdown
122 lines
5.1 KiB
Markdown
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<p align="center">
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<a href="http://gulpjs.com">
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<img height="257" width="114" src="https://raw.githubusercontent.com/gulpjs/artwork/master/gulp-2x.png">
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</a>
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</p>
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# async-done
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[![NPM version][npm-image]][npm-url] [![Downloads][downloads-image]][npm-url] [![Azure Pipelines Build Status][azure-pipelines-image]][azure-pipelines-url] [![Travis Build Status][travis-image]][travis-url] [![AppVeyor Build Status][appveyor-image]][appveyor-url] [![Coveralls Status][coveralls-image]][coveralls-url] [![Gitter chat][gitter-image]][gitter-url]
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Allows libraries to handle various caller provided asynchronous functions uniformly. Maps promises, observables, child processes and streams, and callbacks to callback style.
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As async conventions evolve, it is useful to be able to deal with several different *styles* of async completion uniformly. With this module you can handle completion using a node-style callback, regardless of a return value that's a promise, observable, child process or stream.
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## Usage
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### Successful completion
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```js
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var asyncDone = require('async-done');
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asyncDone(function(done){
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// do async things
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done(null, 2);
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}, function(error, result){
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// `error` will be null on successful execution of the first function.
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// `result` will be the result from the first function.
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});
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```
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### Failed completion
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```js
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var asyncDone = require('async-done');
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asyncDone(function(done){
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// do async things
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done(new Error('Some Error Occurred'));
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}, function(error, result){
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// `error` will be an error from the first function.
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// `result` will be undefined on failed execution of the first function.
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});
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```
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## API
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### `asyncDone(fn, callback)`
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Takes a function to execute (`fn`) and a function to call on completion (`callback`).
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#### `fn([done])`
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Optionally takes a callback to call when async tasks are complete.
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#### Completion and Error Resolution
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* `Callback` (`done`) called
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- Completion: called with null error
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- Error: called with non-null error
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* `Stream` or `EventEmitter` returned
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- Completion: [end-of-stream][end-of-stream] module
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- Error: [domains][domains]
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- __Note:__ Only actual streams are supported, not faux-streams; Therefore, modules like [`event-stream`][event-stream] are not supported.
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* `Child Process` returned
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- Completion [end-of-stream][end-of-stream] module
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- Error: [domains][domains]
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* `Promise` returned
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- Completion: [onFulfilled][promise-onfulfilled] method called
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- Error: [onRejected][promise-onrejected] method called
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* `Observable` (e.g. from [RxJS v5][rxjs5-observable] or [RxJS v4][rxjs5-observable]) returned
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- Completion: [complete][rxjs5-observer-complete] method called
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- Error: [error][rxjs5-observer-error] method called
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__Warning:__ Sync tasks are __not supported__ and your function will never complete if the one of the above strategies is not used to signal completion. However, thrown errors will be caught by the domain.
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#### `callback(error, result)`
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If an error doesn't occur in the execution of the `fn` function, the `callback` method will receive the results as its second argument. Note: Some streams don't received any results.
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If an error occurred in the execution of the `fn` function, The `callback` method will receive an error as its first argument.
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Errors can be caused by:
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* A thrown error
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* An error passed to a `done` callback
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* An `error` event emitted on a returned `Stream`, `EventEmitter` or `Child Process`
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* A rejection of a returned `Promise` - If the `Promise` is not rejected with a value, we generate a new `Error`
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* The `onError` handler being called on an `Observable`
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## License
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MIT
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[downloads-image]: https://img.shields.io/npm/dm/async-done.svg
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[npm-url]: https://www.npmjs.com/package/async-done
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[npm-image]: https://img.shields.io/npm/v/async-done.svg
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[azure-pipelines-url]: https://dev.azure.com/gulpjs/gulp/_build/latest?definitionId=6&branchName=master
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[azure-pipelines-image]: https://dev.azure.com/gulpjs/gulp/_apis/build/status/async-done?branchName=master
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[travis-url]: https://travis-ci.org/gulpjs/async-done
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[travis-image]: https://img.shields.io/travis/gulpjs/async-done.svg?label=travis-ci
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[appveyor-url]: https://ci.appveyor.com/project/gulpjs/async-done
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[appveyor-image]: https://img.shields.io/appveyor/ci/gulpjs/async-done.svg?label=appveyor
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[coveralls-url]: https://coveralls.io/r/gulpjs/async-done
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[coveralls-image]: https://img.shields.io/coveralls/gulpjs/async-done/master.svg
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[gitter-url]: https://gitter.im/gulpjs/gulp
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[gitter-image]: https://badges.gitter.im/gulpjs/gulp.svg
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[end-of-stream]: https://www.npmjs.com/package/end-of-stream
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[domains]: http://nodejs.org/api/domain.html
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[event-stream]: https://github.com/dominictarr/event-stream
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[promise-onfulfilled]: http://promisesaplus.com/#point-26
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[promise-onrejected]: http://promisesaplus.com/#point-30
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[rx4-observable]: https://github.com/Reactive-Extensions/RxJS/blob/master/doc/api/core/observable.md
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[rxjs5-observable]: http://reactivex.io/rxjs/class/es6/Observable.js~Observable.html
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[rxjs5-observer-complete]: http://reactivex.io/rxjs/class/es6/MiscJSDoc.js~ObserverDoc.html#instance-method-complete
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[rxjs5-observer-error]: http://reactivex.io/rxjs/class/es6/MiscJSDoc.js~ObserverDoc.html#instance-method-error
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