# async-done [![NPM version][npm-image]][npm-url] [![Downloads][downloads-image]][npm-url] [![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] Force async using `nextTick` and normalize completion/errors for callbacks, promises, observables, child processes and streams. ## Usage ### Successful completion ```js var asyncDone = require('async-done'); asyncDone(function(done){ // do async things done(null, 2); }, function(error, result){ // `error` will be null on successful execution of the first function. // `result` will be the result from the first function. }); ``` ### Failed completion ```js var asyncDone = require('async-done'); asyncDone(function(done){ // do async things done(new Error('Some Error Occurred')); }, function(error, result){ // `error` will be an error from the first function. // `result` will be undefined on failed execution of the first function. }); ``` ## API ### `asyncDone(fn, callback)` Takes a function to execute (`fn`) and a function to call on completion (`callback`). #### `fn([done])` Optionally takes a callback to call when async tasks are complete. #### Completion and Error Resolution * `Callback` (`done`) called - Completion: called with null error - Error: called with non-null error * `Stream` or `EventEmitter` returned - Completion: [end-of-stream][end-of-stream] module - Error: [domains][domains] - __Note:__ Only actual streams are supported, not faux-streams; Therefore, modules like [`event-stream`][event-stream] are not supported. * `Child Process` returned - Completion [end-of-stream][end-of-stream] module - Error: [domains][domains] * `Promise` returned - Completion: [onFulfilled][promise-onfulfilled] method called - Error: [onRejected][promise-onrejected] method called * `Observable` returned - Completion: [onCompleted][observable-subscribe] method called - Error: [onError][observable-subscribe] method called __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. #### `callback(error, result)` 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: Observable and some streams don't received any results. If an error occurred in the execution of the `fn` function, The `callback` method will receive an error as its first argument. Errors can be caused by: * A thrown error * An error passed to a `done` callback * An `error` event emitted on a returned `Stream`, `EventEmitter` or `Child Process` * A rejection of a returned `Promise` * The `onError` handler being called on an `Observable` ## License MIT [end-of-stream]: https://www.npmjs.com/package/end-of-stream [domains]: http://nodejs.org/api/domain.html [event-stream]: https://github.com/dominictarr/event-stream [promise-onfulfilled]: http://promisesaplus.com/#point-26 [promise-onrejected]: http://promisesaplus.com/#point-30 [observable-subscribe]: https://github.com/Reactive-Extensions/RxJS/blob/master/doc/api/core/operators/subscribe.md [downloads-image]: http://img.shields.io/npm/dm/async-done.svg [npm-url]: https://www.npmjs.com/package/async-done [npm-image]: http://img.shields.io/npm/v/async-done.svg [travis-url]: https://travis-ci.org/gulpjs/async-done [travis-image]: http://img.shields.io/travis/gulpjs/async-done.svg?label=travis-ci [appveyor-url]: https://ci.appveyor.com/project/gulpjs/async-done [appveyor-image]: https://img.shields.io/appveyor/ci/gulpjs/async-done.svg?label=appveyor [coveralls-url]: https://coveralls.io/r/gulpjs/async-done [coveralls-image]: http://img.shields.io/coveralls/gulpjs/async-done/master.svg [gitter-url]: https://gitter.im/gulpjs/gulp [gitter-image]: https://badges.gitter.im/gulpjs/gulp.svg