async-done
Allows libraries to handle various caller provided asynchronous functions uniformly. Maps promises, observables, child processes and streams, and callbacks to callback style.
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.
Usage
Successful completion
var asyncDone = require('async-done');
asyncDone(
function (done) {
done(null, 2);
},
function (error, result) {
}
);
Failed completion
var asyncDone = require('async-done');
asyncDone(
function (done) {
done(new Error('Some Error Occurred'));
},
function (error, result) {
}
);
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 module
- Error: domains
- Note: Only actual streams are supported, not faux-streams; Therefore, modules like
event-stream
are not supported.
Child Process
returned
Promise
returned
Observable
(e.g. from RxJS v5 or RxJS v4) returned
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: 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
- If the Promise
is not rejected with a value, we generate a new Error
- The
onError
handler being called on an Observable
License
MIT