async v3.0.0 Release Notes
Release Date: 2019-05-20 // almost 5 years ago-
๐ The
async
/await
release!There are a lot of new features and subtle breaking changes in this major version, but the biggest feature is that most Async methods return a Promise if you omit the callback, meaning you can
await
them from within anasync
function.const results = await async.mapLimit(urls, 5, async url => { const resp = await fetch(url) return resp.body })
๐ฅ Breaking Changes
- Most Async methods return a Promise when the final callback is omitted, making them
await
-able! (#1572) - ๐ป We are now making heavy use of ES2015 features, this means we have dropped out-of-the-box support for Node 4 and earlier, and many old versions of browsers. (#1541, #1553)
- ๐
In
queue
,priorityQueue
,cargo
andcargoQueue
, the "event"-style methods, likeq.drain
andq.saturated
are now methods that register a callback, rather than properties you assign a callback to. They are now of the formq.drain(callback)
. If you do not pass a callback a Promise will be returned for the next occurrence of the event, making themawait
-able, e.g.await q.drain()
. (#1586, #1641) - Calling
callback(false)
will cancel an async method, preventing further iteration and callback calls. This is useful for preventing memory leaks when you break out of an async flow by calling an outer callback. (#1064, #1542) - ๐
during
anddoDuring
have been removed, and insteadwhilst
,doWhilst
,until
anddoUntil
now have asynchronoustest
functions. (#850, #1557) limits
of less than 1 now cause an error to be thrown in queues and collection methods. (#1249, #1552)memoize
no longer memoizes errors (#1465, #1466)applyEach
/applyEachSeries
have a simpler interface, to make them more easily type-able. It always returns a function that takes in a single callback argument. If that callback is omitted, a promise is returned, making it awaitable. (#1228, #1640)
๐ New Features
- ๐ Async generators are now supported in all the Collection methods. (#1560)
- โ Added
cargoQueue
, a queue with bothconcurrency
andpayload
size parameters. (#1567) - Queue objects returned from
queue
now have aSymbol.iterator
method, meaning they can be iterated over to inspect the current list of items in the queue. (#1459, #1556) - ๐ฆ A ESM-flavored
async.mjs
is included in theasync
package. This is described in thepackage.json
"module"
field, meaning it should be automatically used by Webpack and other compatible bundlers.
๐ Bug fixes
- ๐ Better handle arbitrary error objects in
asyncify
(#1568, #1569)
Other
- โ Removed Lodash as a dependency (#1283, #1528)
- ๐ Miscellaneous docs fixes (#1393, #1501, #1540, #1543, #1558, #1563, #1564, #1579, #1581)
- โ Miscellaneous test fixes (#1538)
- Most Async methods return a Promise when the final callback is omitted, making them