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/*
usage:
asyncMap(myListOfStuff, function (thing, cb) { doSomething(thing, cb) }, cb)
asyncMap(list, function (l, cb) { foo(l, cb) ; bar(l, cb) }, 2, cb)
*/
module.exports = asyncMap
function asyncMap (list, fn, n, cb_) {
if (typeof n === "function") cb_ = n, n = 1
if (typeof cb_ !== "function") throw new Error(
"No callback provided to asyncMap")
if (!list || !list.length) return cb_(null, [])
var data = []
, errState = null
, l = list.length
, a = l * n
function cb (er, d) {
if (errState) return
if (arguments.length > 1) data = data.concat(d)
// see if any new things have been added.
if (list.length > l) {
var newList = list.slice(l)
a += (list.length - l) * n
l = list.length
process.nextTick(function () {
newList.forEach(function (ar) { fn(ar, cb) })
})
}
if (er) {
if (false === cb_(errState = er, data)) errState = null
} else if (-- a === 0) cb_(errState, data)
}
list.forEach(function (ar) { fn(ar, cb) })
}
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