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todo: ordered async-map function

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1 parent 159d28e commit bf9474570f3934f7a7484d6dede596abd7bf35d1 @isaacs isaacs committed Jul 27, 2011
Showing with 65 additions and 0 deletions.
  1. +65 −0 lib/async-map-ordered.js
@@ -0,0 +1,65 @@
+
+throw new Error("TODO: Not yet implemented.")
+
+/*
+usage:
+
+Like asyncMap, but only can take a single cb, and guarantees
+the order of the results.
+*/
+
+module.exports = asyncMapOrdered
+
+function asyncMapOrdered (list, fn, cb_) {
+ if (typeof cb_ !== "function") throw new Error(
+ "No callback provided to asyncMapOrdered")
+
+ if (typeof fn !== "function") throw new Error(
+ "No map function provided to asyncMapOrdered")
+
+ if (list === undefined || list === null) return cb_(null, [])
+ if (!Array.isArray(list)) list = [list]
+ if (!list.length) return cb_(null, [])
+
+ var errState = null
+ , l = list.length
+ , a = l
+ , res = []
+ , resCount = 0
+ , maxArgLen = 0
+
+ function cb (index) { return function () {
+ if (errState) return
+ var er = arguments[0]
+ var argLen = arguments.length
+ maxArgLen = Math.max(maxArgLen, argLen)
+ res[index] = argLen === 1 ? [er] : Array.apply(null, arguments)
+
+ // see if any new things have been added.
+ if (list.length > l) {
+ var newList = list.slice(l)
+ a += (list.length - l)
+ var oldLen = l
+ l = list.length
+ process.nextTick(function () {
+ newList.forEach(function (ar, i) { fn(ar, cb(i + oldLen)) })
+ })
+ }
+
+ if (er || --a === 0) {
+ errState = er
+ cb_.apply(null, [errState].concat(flip(res, resCount, maxArgLen)))
+ }
+ }}
+ // expect the supplied cb function to be called
+ // "n" times for each thing in the array.
+ list.forEach(function (ar) {
+ steps.forEach(function (fn, i) { fn(ar, cb(i)) })
+ })
+}
+
+function flip (res, resCount, argLen) {
+ var flat = []
+ // res = [[er, x, y], [er, x1, y1], [er, x2, y2, z2]]
+ // return [[x, x1, x2], [y, y1, y2], [undefined, undefined, z2]]
+

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