From b26b205f1551e4c89651b279aeb54c6e5ae3e86c Mon Sep 17 00:00:00 2001
From: Benjamin Gruenbaum <inglor@gmail.com>
Date: Mon, 29 Aug 2016 16:34:42 +0300
Subject: [PATCH] Don't allocate an additional array in Promise.each

Closes #1057
---
 src/each.js   |  9 +++++----
 src/map.js    |  3 +--
 src/reduce.js | 16 +++++++++++++---
 3 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/src/each.js b/src/each.js
index ac8ead77f..e4f3d05ba 100644
--- a/src/each.js
+++ b/src/each.js
@@ -12,8 +12,8 @@ function PromiseMapSeries(promises, fn) {
 }
 
 Promise.prototype.each = function (fn) {
-    return this.mapSeries(fn)
-            ._then(promiseAllThis, undefined, undefined, this, undefined);
+    return PromiseReduce(this, fn, INTERNAL, 0)
+              ._then(promiseAllThis, undefined, undefined, this, undefined);
 };
 
 Promise.prototype.mapSeries = function (fn) {
@@ -21,9 +21,10 @@ Promise.prototype.mapSeries = function (fn) {
 };
 
 Promise.each = function (promises, fn) {
-    return PromiseMapSeries(promises, fn)
-            ._then(promiseAllThis, undefined, undefined, promises, undefined);
+    return PromiseReduce(promises, fn, INTERNAL, 0)
+              ._then(promiseAllThis, undefined, undefined, promises, undefined);
 };
 
 Promise.mapSeries = PromiseMapSeries;
 };
+
diff --git a/src/map.js b/src/map.js
index 794c3ec22..d2bf918be 100644
--- a/src/map.js
+++ b/src/map.js
@@ -10,7 +10,6 @@ var getDomain = Promise._getDomain;
 var util = require("./util");
 var tryCatch = util.tryCatch;
 var errorObj = util.errorObj;
-var EMPTY_ARRAY = [];
 
 function MappingPromiseArray(promises, fn, limit, _filter) {
     this.constructor$(promises);
@@ -22,7 +21,7 @@ function MappingPromiseArray(promises, fn, limit, _filter) {
         : null;
     this._limit = limit;
     this._inFlight = 0;
-    this._queue = limit >= 1 ? [] : EMPTY_ARRAY;
+    this._queue = [];
     this._init$(undefined, RESOLVE_ARRAY);
 }
 util.inherits(MappingPromiseArray, PromiseArray);
diff --git a/src/reduce.js b/src/reduce.js
index d2acf0513..76f31eb07 100644
--- a/src/reduce.js
+++ b/src/reduce.js
@@ -19,20 +19,30 @@ function ReductionPromiseArray(promises, fn, initialValue, _each) {
     }
     this._initialValue = initialValue;
     this._currentCancellable = null;
-    this._eachValues = _each === INTERNAL ? [] : undefined;
+    if(_each === INTERNAL) {
+        this._eachValues = Array(this._length);
+    } else if (_each === 0) {
+        this._eachValues = null;
+    } else {
+        this._eachValues = undefined;
+    }
     this._promise._captureStackTrace();
     this._init$(undefined, RESOLVE_CALL_METHOD);
 }
 util.inherits(ReductionPromiseArray, PromiseArray);
 
 ReductionPromiseArray.prototype._gotAccum = function(accum) {
-    if (this._eachValues !== undefined && accum !== INTERNAL) {
+    if (this._eachValues !== undefined && 
+        this._eachValues !== undefined && 
+        accum !== INTERNAL) {
         this._eachValues.push(accum);
     }
 };
 
 ReductionPromiseArray.prototype._eachComplete = function(value) {
-    this._eachValues.push(value);
+    if (this._eachValues !== null) {
+        this._eachValues.push(value);
+    }
     return this._eachValues;
 };