Wait to call the final callback until all subtasks have returned.
Yep, that's it. As of this writing this 'library' is 17 lines of code. You can initialize it on a target callback, and then you can create subtasks of that one. When all the subtasks have completed it will call the target callback.
It supports the node convention of (err, data). If any of your subtasks return results they will be accumulated in an array. If any return an error, the target will be called immediately with the error, and the results of all further subtasks will be ignored.
should = require 'should'accumulator = require '../lib/accumulator'describe 'accumulator', ->it 'should wait for all collectors to return', (done) ->collector = accumulator donesetTimeout collector(), 1setTimeout collector(), 2setTimeout collector(), 3it 'should return all results', (done) ->collector = accumulator (err, results) ->should.not.exist errresults.should.eql [0, 1]done()i = 0doStuff = (cb) ->-> cb null, i++setTimeout doStuff(collector()), 1setTimeout doStuff(collector()), 2
I use Async for some stuff. Async is complex. I've seen promises, but they look a little bit too low level. This is like promises, but a very special case. This happens to be the case that I find myself needing about 80% of the time, and I wanted something very simple to use, very simple to think about and maintain.
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