| 1 | /**
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| 2 | * Copyright (c) 2015-present, Facebook, Inc.
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| 3 | *
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| 4 | * This source code is licensed under the MIT license found in the
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| 5 | * LICENSE file in the root directory of this source tree.
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| 6 | *
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| 7 | * strict
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| 8 | */
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| 9 | import isPromise from './isPromise';
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| 10 |
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| 11 | /**
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| 12 | * Similar to Array.prototype.reduce(), however the reducing callback may return
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| 13 | * a Promise, in which case reduction will continue after each promise resolves.
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| 14 | *
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| 15 | * If the callback does not return a Promise, then this function will also not
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| 16 | * return a Promise.
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| 17 | */
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| 18 | export default function promiseReduce(values, callback, initialValue) {
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| 19 | return values.reduce(function (previous, value) {
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| 20 | return isPromise(previous) ? previous.then(function (resolved) {
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| 21 | return callback(resolved, value);
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| 22 | }) : callback(previous, value);
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| 23 | }, initialValue);
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| 24 | } |
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