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reduce function for async reductions on arrays.


var reduce = require('async-reduce')
function sum(a, b, cb) {
  setTimeout(function() {
    cb(null, a + b)
reduce([1, 2, 3], 1, sum, function(err, result) {

Concurrent reductions are also supported

var reduce = require('async-reduce').concurrent(2, 0, function(a, b) {
  return a + b
reduce([1, 2, 3], 1, sum, function(err, result) {
  result.should.equal(7) // still the same result 

During such reduction the given array is splitted into several chunks with total chunks number equal to concurrency level (it is the first arg to .concurrent()). That chunks are reduced in parallel. That means that we need a combine function to assembel results from that independent reductions (third arg). We also need some sort of unit value to seed our reductions (second arg). But we can omit unit and combine if we only interested in side effects:

var reduce = require('async-reduce').concurrent(5)
var items = []
reduce([1, 2, 3], null, function(_, item, cb) {
}, function(err) {

This lib takes care about sync callback calls. They do not cause stack overflows.


via component

component install eldargab/async-reduce

via npm

npm install async-reduce