1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
|
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>reduce.js - Documentation</title>
<link rel="icon" href="favicon.ico?v=2">
<link rel="stylesheet" href="https://cdn.jsdelivr.net/bootstrap/3.3.6/css/bootstrap.min.css">
<link rel="stylesheet" href="styles/prettify-tomorrow.css">
<link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Montserrat:400,700">
<link rel="stylesheet" href="styles/jsdoc-default.css">
<!--[if lt IE 9]>
<script src="//html5shiv.googlecode.com/svn/trunk/html5.js"></script>
<![endif]-->
<link type="text/css" rel="stylesheet" href="https://cdn.jsdelivr.net/ionicons/2.0.1/css/ionicons.min.css">
</head>
<body>
<div class="navbar navbar-default navbar-fixed-top">
<div class="navbar-header">
<a class="navbar-brand" href="../">
<img src="img/async-logo.svg" alt="Async.js">
</a>
</div>
<ul class="nav navbar-nav">
<li id="version-dropdown" class="dropdown">
<a href="#" class="dropdown-toggle vertically-centered" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">v3.2.4 <span class="caret"></span>
</a>
<ul class="dropdown-menu">
<li><a href="../v3/">v3.0.x</a></li>
<li><a href="../v2/">v2.6.2</a></li>
<li>
<a href="https://github.com/caolan/async/blob/v1.5.2/README.md">v1.5.x</a>
</li>
</ul>
</li>
<li><a href="./index.html">Home</a></li>
<li><a href="./docs.html">Docs</a></li>
<li><a href="https://github.com/caolan/async/blob/master/CHANGELOG.md">Changelog</a></li>
<li><a href="https://github.com/caolan/async"><i class="ion-social-github" aria-hidden="true"></i></a></li>
</ul>
<ul class="nav navbar-nav navbar-right">
<form class="navbar-form navbar-left" role="search">
<div class="form-group">
<input type="text" class="form-control typeahead" id="doc-search" placeholder="Search" autofocus>
</div>
</form>
</ul>
</div>
<input type="checkbox" id="nav-trigger" class="nav-trigger">
<label for="nav-trigger" class="navicon-button x">
<div class="navicon"></div>
</label>
<label for="nav-trigger" class="overlay"></label>
<div id="main">
<div id="main-container" data-spy="scroll" data-target="#toc" data-offset="50">
<h1 class="page-title">reduce.js</h1>
<section>
<article>
<pre class="prettyprint source linenums"><code>import eachOfSeries from './eachOfSeries.js'
import once from './internal/once.js'
import wrapAsync from './internal/wrapAsync.js'
import awaitify from './internal/awaitify.js'
/**
* Reduces `coll` into a single value using an async `iteratee` to return each
* successive step. `memo` is the initial state of the reduction. This function
* only operates in series.
*
* For performance reasons, it may make sense to split a call to this function
* into a parallel map, and then use the normal `Array.prototype.reduce` on the
* results. This function is for situations where each step in the reduction
* needs to be async; if you can get the data before reducing it, then it's
* probably a good idea to do so.
*
* @name reduce
* @static
* @memberOf module:Collections
* @method
* @alias inject
* @alias foldl
* @category Collection
* @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
* @param {*} memo - The initial state of the reduction.
* @param {AsyncFunction} iteratee - A function applied to each item in the
* array to produce the next step in the reduction.
* The `iteratee` should complete with the next state of the reduction.
* If the iteratee completes with an error, the reduction is stopped and the
* main `callback` is immediately called with the error.
* Invoked with (memo, item, callback).
* @param {Function} [callback] - A callback which is called after all the
* `iteratee` functions have finished. Result is the reduced value. Invoked with
* (err, result).
* @returns {Promise} a promise, if no callback is passed
* @example
*
* // file1.txt is a file that is 1000 bytes in size
* // file2.txt is a file that is 2000 bytes in size
* // file3.txt is a file that is 3000 bytes in size
* // file4.txt does not exist
*
* const fileList = ['file1.txt','file2.txt','file3.txt'];
* const withMissingFileList = ['file1.txt','file2.txt','file3.txt', 'file4.txt'];
*
* // asynchronous function that computes the file size in bytes
* // file size is added to the memoized value, then returned
* function getFileSizeInBytes(memo, file, callback) {
* fs.stat(file, function(err, stat) {
* if (err) {
* return callback(err);
* }
* callback(null, memo + stat.size);
* });
* }
*
* // Using callbacks
* async.reduce(fileList, 0, getFileSizeInBytes, function(err, result) {
* if (err) {
* console.log(err);
* } else {
* console.log(result);
* // 6000
* // which is the sum of the file sizes of the three files
* }
* });
*
* // Error Handling
* async.reduce(withMissingFileList, 0, getFileSizeInBytes, function(err, result) {
* if (err) {
* console.log(err);
* // [ Error: ENOENT: no such file or directory ]
* } else {
* console.log(result);
* }
* });
*
* // Using Promises
* async.reduce(fileList, 0, getFileSizeInBytes)
* .then( result => {
* console.log(result);
* // 6000
* // which is the sum of the file sizes of the three files
* }).catch( err => {
* console.log(err);
* });
*
* // Error Handling
* async.reduce(withMissingFileList, 0, getFileSizeInBytes)
* .then( result => {
* console.log(result);
* }).catch( err => {
* console.log(err);
* // [ Error: ENOENT: no such file or directory ]
* });
*
* // Using async/await
* async () => {
* try {
* let result = await async.reduce(fileList, 0, getFileSizeInBytes);
* console.log(result);
* // 6000
* // which is the sum of the file sizes of the three files
* }
* catch (err) {
* console.log(err);
* }
* }
*
* // Error Handling
* async () => {
* try {
* let result = await async.reduce(withMissingFileList, 0, getFileSizeInBytes);
* console.log(result);
* }
* catch (err) {
* console.log(err);
* // [ Error: ENOENT: no such file or directory ]
* }
* }
*
*/
function reduce(coll, memo, iteratee, callback) {
callback = once(callback);
var _iteratee = wrapAsync(iteratee);
return eachOfSeries(coll, (x, i, iterCb) => {
_iteratee(memo, x, (err, v) => {
memo = v;
iterCb(err);
});
}, err => callback(err, memo));
}
export default awaitify(reduce, 4)
</code></pre>
</article>
</section>
<footer>
Documentation generated by <a href="https://github.com/jsdoc3/jsdoc">JSDoc 3.6.2</a> using the Minami theme.
</footer></div>
</div>
<nav id="toc">
<h3>Methods:</h3><ul class="nav methods"><li class="toc-header"><a href="docs.html#collections">Collections</a></li><li data-type="method" class="toc-method"><a href="docs.html#concat">concat</a></li><li data-type="method" class="toc-method"><a href="docs.html#concatLimit">concatLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#concatSeries">concatSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#detect">detect</a></li><li data-type="method" class="toc-method"><a href="docs.html#detectLimit">detectLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#detectSeries">detectSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#each">each</a></li><li data-type="method" class="toc-method"><a href="docs.html#eachLimit">eachLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#eachOf">eachOf</a></li><li data-type="method" class="toc-method"><a href="docs.html#eachOfLimit">eachOfLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#eachOfSeries">eachOfSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#eachSeries">eachSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#every">every</a></li><li data-type="method" class="toc-method"><a href="docs.html#everyLimit">everyLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#everySeries">everySeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#filter">filter</a></li><li data-type="method" class="toc-method"><a href="docs.html#filterLimit">filterLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#filterSeries">filterSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#groupBy">groupBy</a></li><li data-type="method" class="toc-method"><a href="docs.html#groupByLimit">groupByLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#groupBySeries">groupBySeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#map">map</a></li><li data-type="method" class="toc-method"><a href="docs.html#mapLimit">mapLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#mapSeries">mapSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#mapValues">mapValues</a></li><li data-type="method" class="toc-method"><a href="docs.html#mapValuesLimit">mapValuesLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#mapValuesSeries">mapValuesSeries</a></li><li data-type="method" class="toc-method active"><a href="docs.html#reduce">reduce</a></li><li data-type="method" class="toc-method"><a href="docs.html#reduceRight">reduceRight</a></li><li data-type="method" class="toc-method"><a href="docs.html#reject">reject</a></li><li data-type="method" class="toc-method"><a href="docs.html#rejectLimit">rejectLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#rejectSeries">rejectSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#some">some</a></li><li data-type="method" class="toc-method"><a href="docs.html#someLimit">someLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#someSeries">someSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#sortBy">sortBy</a></li><li data-type="method" class="toc-method"><a href="docs.html#transform">transform</a></li><li class="toc-header"><a href="docs.html#controlflow">Control Flow</a></li><li data-type="method" class="toc-method"><a href="docs.html#applyEach">applyEach</a></li><li data-type="method" class="toc-method"><a href="docs.html#applyEachSeries">applyEachSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#auto">auto</a></li><li data-type="method" class="toc-method"><a href="docs.html#autoInject">autoInject</a></li><li data-type="method" class="toc-method"><a href="docs.html#cargo">cargo</a></li><li data-type="method" class="toc-method"><a href="docs.html#cargoQueue">cargoQueue</a></li><li data-type="method" class="toc-method"><a href="docs.html#compose">compose</a></li><li data-type="method" class="toc-method"><a href="docs.html#doUntil">doUntil</a></li><li data-type="method" class="toc-method"><a href="docs.html#doWhilst">doWhilst</a></li><li data-type="method" class="toc-method"><a href="docs.html#forever">forever</a></li><li data-type="method" class="toc-method"><a href="docs.html#parallel">parallel</a></li><li data-type="method" class="toc-method"><a href="docs.html#parallelLimit">parallelLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#priorityQueue">priorityQueue</a></li><li data-type="method" class="toc-method"><a href="docs.html#queue">queue</a></li><li data-type="method" class="toc-method"><a href="docs.html#race">race</a></li><li data-type="method" class="toc-method"><a href="docs.html#retry">retry</a></li><li data-type="method" class="toc-method"><a href="docs.html#retryable">retryable</a></li><li data-type="method" class="toc-method"><a href="docs.html#seq">seq</a></li><li data-type="method" class="toc-method"><a href="docs.html#series">series</a></li><li data-type="method" class="toc-method"><a href="docs.html#times">times</a></li><li data-type="method" class="toc-method"><a href="docs.html#timesLimit">timesLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#timesSeries">timesSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#tryEach">tryEach</a></li><li data-type="method" class="toc-method"><a href="docs.html#until">until</a></li><li data-type="method" class="toc-method"><a href="docs.html#waterfall">waterfall</a></li><li data-type="method" class="toc-method"><a href="docs.html#whilst">whilst</a></li><li class="toc-header"><a href="docs.html#utils">Utils</a></li><li data-type="method" class="toc-method"><a href="docs.html#apply">apply</a></li><li data-type="method" class="toc-method"><a href="docs.html#asyncify">asyncify</a></li><li data-type="method" class="toc-method"><a href="docs.html#constant">constant</a></li><li data-type="method" class="toc-method"><a href="docs.html#dir">dir</a></li><li data-type="method" class="toc-method"><a href="docs.html#ensureAsync">ensureAsync</a></li><li data-type="method" class="toc-method"><a href="docs.html#log">log</a></li><li data-type="method" class="toc-method"><a href="docs.html#memoize">memoize</a></li><li data-type="method" class="toc-method"><a href="docs.html#nextTick">nextTick</a></li><li data-type="method" class="toc-method"><a href="docs.html#reflect">reflect</a></li><li data-type="method" class="toc-method"><a href="docs.html#reflectAll">reflectAll</a></li><li data-type="method" class="toc-method"><a href="docs.html#setImmediate">setImmediate</a></li><li data-type="method" class="toc-method"><a href="docs.html#timeout">timeout</a></li><li data-type="method" class="toc-method"><a href="docs.html#unmemoize">unmemoize</a></li></ul><h3>Methods:</h3>
</nav>
<br class="clear">
<script src="https://cdn.jsdelivr.net/prettify/0.1/prettify.js"></script>
<script src="https://cdn.jsdelivr.net/jquery/2.2.4/jquery.min.js"></script>
<script src="https://cdn.jsdelivr.net/bootstrap/3.3.6/js/bootstrap.min.js"></script>
<script src="https://cdn.jsdelivr.net/typeahead.js/0.11.1/typeahead.bundle.min.js"></script>
<script>prettyPrint();</script>
<script src="scripts/async.js"></script>
<script src="scripts/linenumber.js" async></script>
<script src="scripts/jsdoc-custom.js" async></script>
</body>
|
