Edit - reduce.js

Edit: reduce.js

"use strict";
module.exports = function(Promise,
                          PromiseArray,
                          apiRejection,
                          tryConvertToPromise,
                          INTERNAL,
                          debug) {
var getDomain = Promise._getDomain;
var util = require("./util");
var tryCatch = util.tryCatch;

ReductionPromiseArray.prototype._gotAccum = function(accum) {
    if (this._eachValues !== undefined && 
        this._eachValues !== null && 
        accum !== INTERNAL) {
        this._eachValues.push(accum);
    }
};

ReductionPromiseArray.prototype._eachComplete = function(value) {
    if (this._eachValues !== null) {
        this._eachValues.push(value);
    }
    return this._eachValues;
};

ReductionPromiseArray.prototype._init = function() {};

ReductionPromiseArray.prototype._resolveEmptyArray = function() {
    this._resolve(this._eachValues !== undefined ? this._eachValues
                                                 : this._initialValue);
};

ReductionPromiseArray.prototype.shouldCopyValues = function () {
    return false;
};

ReductionPromiseArray.prototype._resolve = function(value) {
    this._promise._resolveCallback(value);
    this._values = null;
};

ReductionPromiseArray.prototype._resultCancelled = function(sender) {
    if (sender === this._initialValue) return this._cancel();
    if (this._isResolved()) return;
    this._resultCancelled$();
    if (this._currentCancellable instanceof Promise) {
        this._currentCancellable.cancel();
    }
    if (this._initialValue instanceof Promise) {
        this._initialValue.cancel();
    }
};

ReductionPromiseArray.prototype._iterate = function (values) {
    this._values = values;
    var value;
    var i;
    var length = values.length;
    if (this._initialValue !== undefined) {
        value = this._initialValue;
        i = 0;
    } else {
        value = Promise.resolve(values[0]);
        i = 1;
    }

this._currentCancellable = value;

if (!value.isRejected()) {
        for (; i < length; ++i) {
            var ctx = {
                accum: null,
                value: values[i],
                index: i,
                length: length,
                array: this
            };
            value = value._then(gotAccum, undefined, undefined, ctx, undefined);
        }
    }

if (this._eachValues !== undefined) {
        value = value
            ._then(this._eachComplete, undefined, undefined, this, undefined);
    }
    value._then(completed, completed, undefined, value, this);
};

Promise.prototype.reduce = function (fn, initialValue) {
    return reduce(this, fn, initialValue, null);
};

Promise.reduce = function (promises, fn, initialValue, _each) {
    return reduce(promises, fn, initialValue, _each);
};

function completed(valueOrReason, array) {
    if (this.isFulfilled()) {
        array._resolve(valueOrReason);
    } else {
        array._reject(valueOrReason);
    }
}

function reduce(promises, fn, initialValue, _each) {
    if (typeof fn !== "function") {
        return apiRejection("expecting a function but got " + util.classString(fn));
    }
    var array = new ReductionPromiseArray(promises, fn, initialValue, _each);
    return array.promise();
}

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