pasync

pasync

Version of async that uses promises instead of callbacks. Also includes other asynchronous promise utilities.

var pasync = require('pasync');

function getUserById(id) {
	return new Promise(...);
}

var userIds = [1, 2, 3, 4, 5, 6];

pasync.mapLimit(userIds, 2, getUserById).then(function(users) {
	// ...
});

You can also return values instead of promises from the iterator functions, and these will be converted into resolved promises. Exceptions thrown from iterator functions will be converted into rejected promises.

Additionally, this implements error handling for async functions that don't natively have error handling, such as async.filter .

Implemented Functions

• each
• eachSeries
• eachLimit
• map
• mapSeries
• mapLimit
• filter
• select
• filterSeries
• selectSeries
• reject
• rejectSeries
• reduce
• inject
• foldl
• reduceRight
• foldr
• detect
• detectSeries
• sortBy
• some
• every
• concat
• concatSeries
• series
• parallel
• parallelLimit
• whilst
• doWhilst
• until
• doUntil
• forever
• waterfall
• compose
• seq
• applyEach
• applyEachSeries
• queue
• priorityQueue
• cargo
• auto
• retry
• apply
• nextTick
• times
• timesSeries
• memoize
• unmemoize
• log
• dir

Neo-Async Functions Implemented

• concatLimit
• mapValues
• mapValuesSeries
• mapValuesLimit
• detectLimit
• everySeries
• everyLimit
• filterLimit
• pick
• pickSeries
• pickLimit
• rejectLimit
• selectLimit
• someSeries
• someLimit
• sortBySeries
• sortByLimit
• transform
• transformSeries
• transformLimit
• timesLimit

Functions not implemented

• iterator
• noConflict

Other Utilities

all([promises])

This is similar to ES6's Promise.all(), but with the following differences and enhancements:

• The returned promise has a push(promise) method which allows you to add additional promises to the pool after instantiation. The returned promise only resolves once all promises added to it have resolved. It is an error to try to push a new promise after the returned promise has already resolved.
• Promises may be pushed after the returned promises has rejected. In this case, newly pushed promises are silently ignored.
• The order of the result array is guaranteed to be the order that promises were added.
• The [promise1, promise2, ...] parameter is optional. If not passed (or is an empty array), the returned promise will not resolve immediately; instead it will wait for at least one promise to be pushed.

Use it like this:

var p = pasync.all([ promise1, promise2 ]);
p.then(/* handlers */);
// later ...
p.push(promise3);
p.push(promise4);

abort(err)

This is intended to be used as a last-ditch error handler for promises. Using promises, if the last rejection handler in a promise throws an exception, it is silently ignored. Calling abort(err) will throw err as an exception in the global scope, calling the process's uncaughtException listeners or exiting with the exception by default. Use it like this:

getUser(nonexistent_id).then(function(user) {
	// do something with user
}).catch(function(err) {
	// Note the (obvious) errors in the rejection handlers; by default, this will be silently ignored
	cunsil.lug(err);
}).catch(pasync.abort);	// This will catch the undefined variable error and throw it globally

Contributors

• crispy1989
• crowelch