forked from jashkenas/underscore
-
Notifications
You must be signed in to change notification settings - Fork 0
/
Copy pathindex.html
3399 lines (3124 loc) · 137 KB
/
index.html
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
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="content-type" content="text/html;charset=UTF-8" />
<meta http-equiv="X-UA-Compatible" content="chrome=1" />
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<meta name="viewport" content="target-densitydpi=device-dpi" />
<meta name="HandheldFriendly" content="true"/>
<link rel="canonical" href="http://underscorejs.org/" />
<link rel="shortcut icon" href="favicon.ico" type="image/x-icon" />
<title>Underscore.js</title>
<style>
body {
font-size: 14px;
line-height: 22px;
background: #f4f4f4 url(docs/images/background.png);
color: #000;
font-family: Helvetica Neue, Helvetica, Arial;
}
.interface {
font-family: "Lucida Grande", "Lucida Sans Unicode", Helvetica, Arial, sans-serif !important;
}
div#sidebar {
background: #fff;
position: fixed;
top: 0; left: 0; bottom: 0;
width: 200px;
overflow-y: auto;
overflow-x: hidden;
-webkit-overflow-scrolling: touch;
padding: 15px 0 30px 30px;
border-right: 1px solid #bbb;
box-shadow: 0 0 20px #ccc; -webkit-box-shadow: 0 0 20px #ccc; -moz-box-shadow: 0 0 20px #ccc;
}
a.toc_title, a.toc_title:visited {
display: block;
color: black;
font-weight: bold;
margin-top: 15px;
}
a.toc_title:hover {
text-decoration: underline;
}
#sidebar .version {
font-size: 10px;
font-weight: normal;
}
ul.toc_section {
font-size: 11px;
line-height: 14px;
margin: 5px 0 0 0;
padding-left: 0px;
list-style-type: none;
}
.toc_section li {
cursor: pointer;
margin: 0 0 3px 0;
}
.toc_section li a {
text-decoration: none;
color: black;
}
.toc_section li a:hover {
text-decoration: underline;
}
input#function_filter {
width: 80%;
}
div.container {
width: 550px;
margin: 40px 0 50px 260px;
}
img#logo {
width: 396px;
height: 69px;
}
div.warning {
margin-top: 15px;
font: bold 11px Arial;
color: #770000;
}
p {
margin: 20px 0;
width: 550px;
}
a, a:visited {
color: #444;
}
a:active, a:hover {
color: #000;
}
h1, h2, h3, h4, h5, h6 {
padding-top: 20px;
}
h2 {
font-size: 20px;
}
b.header {
font-size: 16px;
line-height: 30px;
}
span.alias {
font-size: 14px;
font-style: italic;
margin-left: 20px;
}
table, tr, td {
margin: 0; padding: 0;
}
td {
padding: 2px 12px 2px 0;
}
table .rule {
height: 1px;
background: #ccc;
margin: 5px 0;
}
ul {
list-style-type: circle;
padding: 0 0 0 20px;
}
li {
margin-bottom: 10px;
}
code, pre, tt {
font-family: Monaco, Consolas, "Lucida Console", monospace;
font-size: 12px;
line-height: 18px;
font-style: normal;
}
tt {
padding: 0px 3px;
background: #fff;
border: 1px solid #ddd;
zoom: 1;
}
code {
margin-left: 20px;
}
pre {
font-size: 12px;
padding: 2px 0 2px 15px;
border-left: 5px solid #bbb;
margin: 0px 0 30px;
}
@media only screen and (-webkit-min-device-pixel-ratio: 1.5) and (max-width: 640px),
only screen and (-o-min-device-pixel-ratio: 3/2) and (max-width: 640px),
only screen and (min-device-pixel-ratio: 1.5) and (max-width: 640px) {
img {
max-width: 100%;
}
div#sidebar {
-webkit-overflow-scrolling: initial;
position: relative;
width: 90%;
height: 120px;
left: 0;
top: -7px;
padding: 10px 0 10px 30px;
border: 0;
}
img#logo {
width: auto;
height: auto;
}
div.container {
margin: 0;
width: 100%;
}
p, div.container ul {
max-width: 98%;
overflow-x: scroll;
}
pre {
overflow: scroll;
}
}
</style>
</head>
<body>
<div id="sidebar" class="interface">
<a class="toc_title" href="#">
Underscore.js <span class="version">(1.9.0)</span>
</a>
<ul class="toc_section">
<li>» <a href="https://github.com/jashkenas/underscore">GitHub Repository</a></li>
<li>» <a href="docs/underscore.html">Annotated Source</a></li>
<li>» <a href="http://documentcloud.github.io/underscore-contrib/">Underscore-contrib</a></li>
</ul>
<input id="function_filter" placeholder="Filter" type="text" autofocus />
<div class="searchable_section">
<a class="toc_title" href="#">
Introduction
</a>
</div>
<div class="searchable_section">
<a class="toc_title" href="#collections">
Collections
</a>
<ul class="toc_section">
<li data-name="each" data-aliases="forEach">- <a href="#each">each</a></li>
<li data-name="map" data-aliases="collect">- <a href="#map">map</a></li>
<li data-name="reduce" data-aliases="inject foldl">- <a href="#reduce">reduce</a></li>
<li data-name="reduceRight" data-aliases="foldr">- <a href="#reduceRight">reduceRight</a></li>
<li data-name="find" data-aliases="detect">- <a href="#find">find</a></li>
<li data-name="filter" data-aliases="select">- <a href="#filter">filter</a></li>
<li data-name="where">- <a href="#where">where</a></li>
<li data-name="findWhere">- <a href="#findWhere">findWhere</a></li>
<li data-name="reject">- <a href="#reject">reject</a></li>
<li data-name="every" data-aliases="all">- <a href="#every">every</a></li>
<li data-name="some" data-aliases="any">- <a href="#some">some</a></li>
<li data-name="contains" data-aliases="include includes">- <a href="#contains">contains</a></li>
<li data-name="invoke">- <a href="#invoke">invoke</a></li>
<li data-name="pluck">- <a href="#pluck">pluck</a></li>
<li data-name="max">- <a href="#max">max</a></li>
<li data-name="min">- <a href="#min">min</a></li>
<li data-name="sortBy">- <a href="#sortBy">sortBy</a></li>
<li data-name="groupBy">- <a href="#groupBy">groupBy</a></li>
<li data-name="indexBy">- <a href="#indexBy">indexBy</a></li>
<li data-name="countBy">- <a href="#countBy">countBy</a></li>
<li data-name="shuffle">- <a href="#shuffle">shuffle</a></li>
<li data-name="sample">- <a href="#sample">sample</a></li>
<li data-name="toArray">- <a href="#toArray">toArray</a></li>
<li data-name="size">- <a href="#size">size</a></li>
<li data-name="partition">- <a href="#partition">partition</a></li>
<li data-name="compact">- <a href="#compact">compact</a></li>
</ul>
</div>
<div class="searchable_section">
<a class="toc_title" href="#arrays">
Arrays
</a>
<ul class="toc_section">
<li data-name="first" data-aliases="head take">- <a href="#first">first</a></li>
<li data-name="initial">- <a href="#initial">initial</a></li>
<li data-name="last">- <a href="#last">last</a></li>
<li data-name="rest" data-aliases="tail drop">- <a href="#rest">rest</a></li>
<li data-name="flatten">- <a href="#flatten">flatten</a></li>
<li data-name="without">- <a href="#without">without</a></li>
<li data-name="union">- <a href="#union">union</a></li>
<li data-name="intersection">- <a href="#intersection">intersection</a></li>
<li data-name="difference">- <a href="#difference">difference</a></li>
<li data-name="uniq" data-aliases="unique">- <a href="#uniq">uniq</a></li>
<li data-name="zip">- <a href="#zip">zip</a></li>
<li data-name="unzip">- <a href="#unzip">unzip</a></li>
<li data-name="object">- <a href="#object">object</a></li>
<li data-name="chunk">- <a href="#chunk">chunk</a></li>
<li data-name="indexOf">- <a href="#indexOf">indexOf</a></li>
<li data-name="lastIndexOf">- <a href="#lastIndexOf">lastIndexOf</a></li>
<li data-name="sortedIndex">- <a href="#sortedIndex">sortedIndex</a></li>
<li data-name="findIndex">- <a href="#findIndex">findIndex</a></li>
<li data-name="findLastIndex">- <a href="#findLastIndex">findLastIndex</a></li>
<li data-name="range">- <a href="#range">range</a></li>
</ul>
</div>
<div class="searchable_section">
<a class="toc_title" href="#functions">
Functions
</a>
<ul class="toc_section">
<li data-name="bind">- <a href="#bind">bind</a></li>
<li data-name="bindAll">- <a href="#bindAll">bindAll</a></li>
<li data-name="partial">- <a href="#partial">partial</a></li>
<li data-name="memoize">- <a href="#memoize">memoize</a></li>
<li data-name="delay">- <a href="#delay">delay</a></li>
<li data-name="defer">- <a href="#defer">defer</a></li>
<li data-name="throttle">- <a href="#throttle">throttle</a></li>
<li data-name="debounce">- <a href="#debounce">debounce</a></li>
<li data-name="once">- <a href="#once">once</a></li>
<li data-name="after">- <a href="#after">after</a></li>
<li data-name="before">- <a href="#before">before</a></li>
<li data-name="wrap">- <a href="#wrap">wrap</a></li>
<li data-name="negate">- <a href="#negate">negate</a></li>
<li data-name="compose">- <a href="#compose">compose</a></li>
<li data-name="restArguments">- <a href="#restArguments">restArguments</a></li>
</ul>
</div>
<div class="searchable_section">
<a class="toc_title" href="#objects">
Objects
</a>
<ul class="toc_section">
<li data-name="keys">- <a href="#keys">keys</a></li>
<li data-name="allKeys">- <a href="#allKeys">allKeys</a></li>
<li data-name="values">- <a href="#values">values</a></li>
<li data-name="mapObject">- <a href="#mapObject">mapObject</a></li>
<li data-name="pairs">- <a href="#pairs">pairs</a></li>
<li data-name="invert">- <a href="#invert">invert</a></li>
<li data-name="create">- <a href="#create">create</a></li>
<li data-name="object-functions" data-aliases="methods">- <a href="#object-functions">functions</a></li>
<li data-name="findKey">- <a href="#findKey">findKey</a></li>
<li data-name="extend">- <a href="#extend">extend</a></li>
<li data-name="extendOwn" data-aliases="assign">- <a href="#extendOwn">extendOwn</a></li>
<li data-name="pick">- <a href="#pick">pick</a></li>
<li data-name="omit">- <a href="#omit">omit</a></li>
<li data-name="defaults">- <a href="#defaults">defaults</a></li>
<li data-name="clone">- <a href="#clone">clone</a></li>
<li data-name="tap">- <a href="#tap">tap</a></li>
<li data-name="has">- <a href="#has">has</a></li>
<li data-name="property">- <a href="#property">property</a></li>
<li data-name="propertyOf">- <a href="#propertyOf">propertyOf</a></li>
<li data-name="matcher">- <a href="#matcher">matcher</a></li>
<li data-name="isEqual">- <a href="#isEqual">isEqual</a></li>
<li data-name="isMatch">- <a href="#isMatch">isMatch</a></li>
<li data-name="isEmpty">- <a href="#isEmpty">isEmpty</a></li>
<li data-name="isElement">- <a href="#isElement">isElement</a></li>
<li data-name="isArray">- <a href="#isArray">isArray</a></li>
<li data-name="isObject">- <a href="#isObject">isObject</a></li>
<li data-name="isArguments">- <a href="#isArguments">isArguments</a></li>
<li data-name="isFunction">- <a href="#isFunction">isFunction</a></li>
<li data-name="isString">- <a href="#isString">isString</a></li>
<li data-name="isNumber">- <a href="#isNumber">isNumber</a></li>
<li data-name="isFinite">- <a href="#isFinite">isFinite</a></li>
<li data-name="isBoolean">- <a href="#isBoolean">isBoolean</a></li>
<li data-name="isDate">- <a href="#isDate">isDate</a></li>
<li data-name="isRegExp">- <a href="#isRegExp">isRegExp</a></li>
<li data-name="isError">- <a href="#isError">isError</a></li>
<li data-name="isSymbol">- <a href="#isSymbol">isSymbol</a></li>
<li data-name="isMap">- <a href="#isMap">isMap</a></li>
<li data-name="isWeakMap">- <a href="#isWeakMap">isWeakMap</a></li>
<li data-name="isSet">- <a href="#isSet">isSet</a></li>
<li data-name="isWeakSet">- <a href="#isWeakSet">isWeakSet</a></li>
<li data-name="isNaN">- <a href="#isNaN">isNaN</a></li>
<li data-name="isNull">- <a href="#isNull">isNull</a></li>
<li data-name="isUndefined">- <a href="#isUndefined">isUndefined</a></li>
</ul>
</div>
<div class="searchable_section">
<a class="toc_title" href="#utility">
Utility
</a>
<ul class="toc_section">
<li data-name="noConflict">- <a href="#noConflict">noConflict</a></li>
<li data-name="identity">- <a href="#identity">identity</a></li>
<li data-name="constant">- <a href="#constant">constant</a></li>
<li data-name="noop">- <a href="#noop">noop</a></li>
<li data-name="times">- <a href="#times">times</a></li>
<li data-name="random">- <a href="#random">random</a></li>
<li data-name="mixin">- <a href="#mixin">mixin</a></li>
<li data-name="iteratee">- <a href="#iteratee">iteratee</a></li>
<li data-name="uniqueId">- <a href="#uniqueId">uniqueId</a></li>
<li data-name="escape">- <a href="#escape">escape</a></li>
<li data-name="unescape">- <a href="#unescape">unescape</a></li>
<li data-name="result">- <a href="#result">result</a></li>
<li data-name="now">- <a href="#now">now</a></li>
<li data-name="template">- <a href="#template">template</a></li>
</ul>
</div>
<div class="searchable_section">
<a class="toc_title" href="#oop">
OOP Style
</a>
</div>
<div class="searchable_section">
<a class="toc_title" href="#chaining">
Chaining
</a>
<ul class="toc_section">
<li data-name="chain">- <a href="#chain">chain</a></li>
<li data-name="value">- <a href="#value">value</a></li>
</ul>
</div>
<div class="searchable_section">
<a class="toc_title" href="#links">
Links
</a>
</div>
<div class="searchable_section">
<a class="toc_title" href="#changelog">
Change Log
</a>
</div>
</div>
<div class="container">
<p id="introduction">
<img id="logo" src="docs/images/underscore.png" alt="Underscore.js" />
</p>
<p>
<a href="http://github.com/jashkenas/underscore/">Underscore</a>
is a JavaScript library that provides a whole mess of useful functional
programming helpers without extending any built-in objects.
It’s the answer to the question: “If I sit down in front of a
blank HTML page, and want to start being productive immediately, what do I need?”
… and the tie to go along with
<a href="http://jquery.com">jQuery</a>'s tux and
<a href="http://backbonejs.org">Backbone</a>'s suspenders.
</p>
<p>
Underscore provides over 100 functions that support both your favorite
workaday functional helpers: <b>map</b>, <b>filter</b>, <b>invoke</b> —
as well as more specialized goodies: function binding, javascript
templating, creating quick indexes, deep equality testing, and so on.
</p>
<p>
A complete <a href="test/">Test Suite</a>
is included for your perusal.
</p>
<p>
You may also read through the <a href="docs/underscore.html">annotated source code</a>.
</p>
<p>
Enjoying Underscore, and want to <i>turn it up to 11?</i> Try <a href="http://documentcloud.github.io/underscore-contrib/">Underscore-contrib</a>.
</p>
<p>
The project is
<a href="https://github.com/jashkenas/underscore">hosted on GitHub</a>.
You can report bugs and discuss features on the
<a href="https://github.com/jashkenas/underscore/issues">issues page</a>,
on Freenode in the <tt>#documentcloud</tt> channel, or in our <a href="https://gitter.im/jashkenas/underscore">Gitter</a>
channel.
</p>
<p>
<i>Underscore is an open-source component of <a href="http://documentcloud.org/">DocumentCloud</a>.</i>
</p>
<h2>Downloads <i style="padding-left: 12px; font-size:12px;">(Right-click, and use "Save As")</i></h2>
<table>
<tr>
<td><a href="underscore.js">Development Version (1.9.0)</a></td>
<td><i>60kb, Uncompressed with Plentiful Comments</i></td>
</tr>
<tr>
<td><a href="underscore-min.js">Production Version (1.9.0)</a></td>
<td>
<i>6.5kb, Minified and Gzipped</i>
<small>(<a href="underscore-min.js.map">Source Map</a>)</small>
</td>
</tr>
<tr>
<td colspan="2"><div class="rule"></div></td>
</tr>
<tr>
<td><a href="https://raw.github.com/jashkenas/underscore/master/underscore.js">Edge Version</a></td>
<td><i>Unreleased, current <tt>master</tt>, use by your own judgement and at your own risk</i></td>
</tr>
</table>
<h2>Installation</h2>
<ul>
<li>
<b>Node.js</b> <tt>npm install underscore</tt>
</li>
<li>
<b>Meteor.js</b> <tt>meteor add underscore</tt>
</li>
<li>
<b>Require.js</b> <tt>require(["underscore"], ...</tt>
</li>
<li>
<b>Bower</b> <tt>bower install underscore</tt>
</li>
<li>
<b>Component</b> <tt>component install jashkenas/underscore</tt>
</li>
</ul>
<div id="documentation">
<h2 id="collections">Collection Functions (Arrays or Objects)</h2>
<p id="each">
<b class="header">each</b><code>_.each(list, iteratee, [context])</code>
<span class="alias">Alias: <b>forEach</b></span>
<br />
Iterates over a <b>list</b> of elements, yielding each in turn to an
<b>iteratee</b> function.
The <b>iteratee</b> is bound to the <b>context</b> object, if one is
passed. Each invocation of <b>iteratee</b> is called with three arguments:
<tt>(element, index, list)</tt>. If <b>list</b> is a JavaScript object, <b>iteratee</b>'s
arguments will be <tt>(value, key, list)</tt>. Returns the <b>list</b> for chaining.
</p>
<pre>
_.each([1, 2, 3], alert);
=> alerts each number in turn...
_.each({one: 1, two: 2, three: 3}, alert);
=> alerts each number value in turn...</pre>
<p>
<i>
Note: Collection functions work on arrays, objects, and
array-like objects such as</i> <tt>arguments</tt>, <tt>NodeList</tt><i>
and similar. But it works by duck-typing, so avoid passing objects with
a numeric <tt>length</tt> property. It's also good to note that an
<tt>each</tt> loop cannot be broken out of — to break, use <b>_.find</b>
instead.
</i>
</p>
<p id="map">
<b class="header">map</b><code>_.map(list, iteratee, [context])</code>
<span class="alias">Alias: <b>collect</b></span>
<br />
Produces a new array of values by mapping each value in <b>list</b>
through a transformation function (<a href="#iteratee"><b>iteratee</b></a>).
The iteratee is passed three arguments: the <tt>value</tt>,
then the <tt>index</tt> (or <tt>key</tt>) of the iteration,
and finally a reference to the entire <tt>list</tt>.
</p>
<pre>
_.map([1, 2, 3], function(num){ return num * 3; });
=> [3, 6, 9]
_.map({one: 1, two: 2, three: 3}, function(num, key){ return num * 3; });
=> [3, 6, 9]
_.map([[1, 2], [3, 4]], _.first);
=> [1, 3]</pre>
<p id="reduce">
<b class="header">reduce</b><code>_.reduce(list, iteratee, [memo], [context])</code>
<span class="alias">Aliases: <b>inject</b>, <b>foldl</b></span>
<br />
Also known as <b>inject</b> and <b>foldl</b>, reduce boils down a <b>list</b> of values into a single value.
<b>Memo</b> is the initial state of the reduction, and each successive step of it should be returned by
<b>iteratee</b>. The iteratee is passed four arguments: the <tt>memo</tt>, then the <tt>value</tt> and
<tt>index</tt> (or key) of the iteration, and finally a reference to the entire <tt>list</tt>.
</p>
<p>
If no memo is passed to the initial invocation of reduce, the iteratee is not invoked on the first element
of the list. The first element is instead passed as the memo in the invocation of the iteratee on the next
element in the list.
</p>
<pre>
var sum = _.reduce([1, 2, 3], function(memo, num){ return memo + num; }, 0);
=> 6
</pre>
<p id="reduceRight">
<b class="header">reduceRight</b><code>_.reduceRight(list, iteratee, [memo], [context])</code>
<span class="alias">Alias: <b>foldr</b></span>
<br />
The right-associative version of <b>reduce</b>. <b>Foldr</b>
is not as useful in JavaScript as it would be in a language with lazy
evaluation.
</p>
<pre>
var list = [[0, 1], [2, 3], [4, 5]];
var flat = _.reduceRight(list, function(a, b) { return a.concat(b); }, []);
=> [4, 5, 2, 3, 0, 1]
</pre>
<p id="find">
<b class="header">find</b><code>_.find(list, predicate, [context])</code>
<span class="alias">Alias: <b>detect</b></span>
<br />
Looks through each value in the <b>list</b>, returning the first one that
passes a truth test (<b>predicate</b>), or <tt>undefined</tt> if no value
passes the test. The function returns as
soon as it finds an acceptable element, and doesn't traverse the
entire list.
<b>predicate</b> is transformed through <a href="#iteratee"><b>iteratee</b></a>
to facilitate shorthand syntaxes.
</p>
<pre>
var even = _.find([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; });
=> 2
</pre>
<p id="filter">
<b class="header">filter</b><code>_.filter(list, predicate, [context])</code>
<span class="alias">Alias: <b>select</b></span>
<br />
Looks through each value in the <b>list</b>, returning an array of all
the values that pass a truth test (<b>predicate</b>).
<b>predicate</b> is transformed through <a href="#iteratee"><b>iteratee</b></a>
to facilitate shorthand syntaxes.
</p>
<pre>
var evens = _.filter([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; });
=> [2, 4, 6]
</pre>
<p id="findWhere">
<b class="header">findWhere</b><code>_.findWhere(list, properties)</code>
<br />
Looks through the <b>list</b> and returns the <i>first</i> value that <a href="#matches">matches</a>
all of the key-value pairs listed in <b>properties</b>.
</p>
<p>
If no match is found, or if <b>list</b> is empty, <i>undefined</i> will be
returned.
</p>
<pre>
_.findWhere(publicServicePulitzers, {newsroom: "The New York Times"});
=> {year: 1918, newsroom: "The New York Times",
reason: "For its public service in publishing in full so many official reports,
documents and speeches by European statesmen relating to the progress and
conduct of the war."}
</pre>
<p id="where">
<b class="header">where</b><code>_.where(list, properties)</code>
<br />
Looks through each value in the <b>list</b>, returning an array of all
the values that <a href="#matches">matches</a> the key-value pairs listed in <b>properties</b>.
</p>
<pre>
_.where(listOfPlays, {author: "Shakespeare", year: 1611});
=> [{title: "Cymbeline", author: "Shakespeare", year: 1611},
{title: "The Tempest", author: "Shakespeare", year: 1611}]
</pre>
<p id="reject">
<b class="header">reject</b><code>_.reject(list, predicate, [context])</code>
<br />
Returns the values in <b>list</b> without the elements that the truth
test (<b>predicate</b>) passes. The opposite of <b>filter</b>.
<b>predicate</b> is transformed through <a href="#iteratee"><b>iteratee</b></a>
to facilitate shorthand syntaxes.
</p>
<pre>
var odds = _.reject([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; });
=> [1, 3, 5]
</pre>
<p id="every">
<b class="header">every</b><code>_.every(list, [predicate], [context])</code>
<span class="alias">Alias: <b>all</b></span>
<br />
Returns <i>true</i> if all of the values in the <b>list</b> pass the
<b>predicate</b> truth test. Short-circuits and stops traversing the list
if a false element is found.
<b>predicate</b> is transformed through <a href="#iteratee"><b>iteratee</b></a>
to facilitate shorthand syntaxes.
</p>
<pre>
_.every([2, 4, 5], function(num) { return num % 2 == 0; });
=> false
</pre>
<p id="some">
<b class="header">some</b><code>_.some(list, [predicate], [context])</code>
<span class="alias">Alias: <b>any</b></span>
<br />
Returns <i>true</i> if any of the values in the <b>list</b> pass the
<b>predicate</b> truth test. Short-circuits and stops traversing the list
if a true element is found.
<b>predicate</b> is transformed through <a href="#iteratee"><b>iteratee</b></a>
to facilitate shorthand syntaxes.
</p>
<pre>
_.some([null, 0, 'yes', false]);
=> true
</pre>
<p id="contains">
<b class="header">contains</b><code>_.contains(list, value, [fromIndex])</code>
<span class="alias">Aliases: <b>include</b>, <b>includes</b></span>
<br />
Returns <i>true</i> if the <b>value</b> is present in the <b>list</b>.
Uses <b>indexOf</b> internally, if <b>list</b> is an Array.
Use <b>fromIndex</b> to start your search at a given index.
</p>
<pre>
_.contains([1, 2, 3], 3);
=> true
</pre>
<p id="invoke">
<b class="header">invoke</b><code>_.invoke(list, methodName, *arguments)</code>
<br />
Calls the method named by <b>methodName</b> on each value in the <b>list</b>.
Any extra arguments passed to <b>invoke</b> will be forwarded on to the
method invocation.
</p>
<pre>
_.invoke([[5, 1, 7], [3, 2, 1]], 'sort');
=> [[1, 5, 7], [1, 2, 3]]
</pre>
<p id="pluck">
<b class="header">pluck</b><code>_.pluck(list, propertyName)</code>
<br />
A convenient version of what is perhaps the most common use-case for
<b>map</b>: extracting a list of property values.
</p>
<pre>
var stooges = [{name: 'moe', age: 40}, {name: 'larry', age: 50}, {name: 'curly', age: 60}];
_.pluck(stooges, 'name');
=> ["moe", "larry", "curly"]
</pre>
<p id="max">
<b class="header">max</b><code>_.max(list, [iteratee], [context])</code>
<br />
Returns the maximum value in <b>list</b>. If an <a href="#iteratee"><b>iteratee</b></a>
function is provided, it will be used on each value to generate the
criterion by which the value is ranked. <i>-Infinity</i> is returned
if <b>list</b> is empty, so an <a href="#isEmpty">isEmpty</a> guard
may be required. Non-numerical values in <b>list</b> will be ignored.
</p>
<pre>
var stooges = [{name: 'moe', age: 40}, {name: 'larry', age: 50}, {name: 'curly', age: 60}];
_.max(stooges, function(stooge){ return stooge.age; });
=> {name: 'curly', age: 60};
</pre>
<p id="min">
<b class="header">min</b><code>_.min(list, [iteratee], [context])</code>
<br />
Returns the minimum value in <b>list</b>. If an <a href="#iteratee"><b>iteratee</b></a>
function is provided, it will be used on each value to generate the
criterion by which the value is ranked. <i>Infinity</i> is returned
if <b>list</b> is empty, so an <a href="#isEmpty">isEmpty</a> guard
may be required. Non-numerical values in <b>list</b> will be ignored.
</p>
<pre>
var numbers = [10, 5, 100, 2, 1000];
_.min(numbers);
=> 2
</pre>
<p id="sortBy">
<b class="header">sortBy</b><code>_.sortBy(list, iteratee, [context])</code>
<br />
Returns a (stably) sorted copy of <b>list</b>, ranked in ascending
order by the results of running each value through <a href="#iteratee"><b>iteratee</b></a>.
iteratee may also be the string name of the property to sort by (eg.
<tt>length</tt>).
</p>
<pre>
_.sortBy([1, 2, 3, 4, 5, 6], function(num){ return Math.sin(num); });
=> [5, 4, 6, 3, 1, 2]
var stooges = [{name: 'moe', age: 40}, {name: 'larry', age: 50}, {name: 'curly', age: 60}];
_.sortBy(stooges, 'name');
=> [{name: 'curly', age: 60}, {name: 'larry', age: 50}, {name: 'moe', age: 40}];
</pre>
<p id="groupBy">
<b class="header">groupBy</b><code>_.groupBy(list, iteratee, [context])</code>
<br />
Splits a collection into sets, grouped by the result of running each
value through <b>iteratee</b>. If <b>iteratee</b> is a string instead of
a function, groups by the property named by <b>iteratee</b> on each of
the values.
</p>
<pre>
_.groupBy([1.3, 2.1, 2.4], function(num){ return Math.floor(num); });
=> {1: [1.3], 2: [2.1, 2.4]}
_.groupBy(['one', 'two', 'three'], 'length');
=> {3: ["one", "two"], 5: ["three"]}
</pre>
<p id="indexBy">
<b class="header">indexBy</b><code>_.indexBy(list, iteratee, [context])</code>
<br />
Given a <b>list</b>, and an <a href="#iteratee"><b>iteratee</b></a> function
that returns a key for each element in the list (or a property name),
returns an object with an index of each item.
Just like <a href="#groupBy">groupBy</a>, but for when you know your
keys are unique.
</p>
<pre>
var stooges = [{name: 'moe', age: 40}, {name: 'larry', age: 50}, {name: 'curly', age: 60}];
_.indexBy(stooges, 'age');
=> {
"40": {name: 'moe', age: 40},
"50": {name: 'larry', age: 50},
"60": {name: 'curly', age: 60}
}
</pre>
<p id="countBy">
<b class="header">countBy</b><code>_.countBy(list, iteratee, [context])</code>
<br />
Sorts a list into groups and returns a count for the number of objects
in each group.
Similar to <tt>groupBy</tt>, but instead of returning a list of values,
returns a count for the number of values in that group.
</p>
<pre>
_.countBy([1, 2, 3, 4, 5], function(num) {
return num % 2 == 0 ? 'even': 'odd';
});
=> {odd: 3, even: 2}
</pre>
<p id="shuffle">
<b class="header">shuffle</b><code>_.shuffle(list)</code>
<br />
Returns a shuffled copy of the <b>list</b>, using a version of the
<a href="http://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle">Fisher-Yates shuffle</a>.
</p>
<pre>
_.shuffle([1, 2, 3, 4, 5, 6]);
=> [4, 1, 6, 3, 5, 2]
</pre>
<p id="sample">
<b class="header">sample</b><code>_.sample(list, [n])</code>
<br />
Produce a random sample from the <b>list</b>. Pass a number to
return <b>n</b> random elements from the list. Otherwise a single random
item will be returned.
</p>
<pre>
_.sample([1, 2, 3, 4, 5, 6]);
=> 4
_.sample([1, 2, 3, 4, 5, 6], 3);
=> [1, 6, 2]
</pre>
<p id="toArray">
<b class="header">toArray</b><code>_.toArray(list)</code>
<br />
Creates a real Array from the <b>list</b> (anything that can be
iterated over). Useful for transmuting the <b>arguments</b> object.
</p>
<pre>
(function(){ return _.toArray(arguments).slice(1); })(1, 2, 3, 4);
=> [2, 3, 4]
</pre>
<p id="size">
<b class="header">size</b><code>_.size(list)</code>
<br />
Return the number of values in the <b>list</b>.
</p>
<pre>
_.size([1, 2, 3, 4, 5]);
=> 5
_.size({one: 1, two: 2, three: 3});
=> 3
</pre>
<p id="partition">
<b class="header">partition</b><code>_.partition(list, predicate)</code>
<br />
Split <b>list</b> into two arrays: one whose elements all satisfy
<b>predicate</b> and one whose elements all do not satisfy <b>predicate</b>.
<b>predicate</b> is transformed through <a href="#iteratee"><b>iteratee</b></a>
to facilitate shorthand syntaxes.
</p>
<pre>
_.partition([0, 1, 2, 3, 4, 5], isOdd);
=> [[1, 3, 5], [0, 2, 4]]
</pre>
<p id="compact">
<b class="header">compact</b><code>_.compact(list)</code>
<br />
Returns a copy of the <b>list</b> with all falsy values removed.
In JavaScript, <i>false</i>, <i>null</i>, <i>0</i>, <i>""</i>,
<i>undefined</i> and <i>NaN</i> are all falsy.
</p>
<pre>
_.compact([0, 1, false, 2, '', 3]);
=> [1, 2, 3]
</pre>
<h2 id="arrays">Array Functions</h2>
<p>
<i>
Note: All array functions will also work on the <b>arguments</b> object.
However, Underscore functions are not designed to work on "sparse" arrays.
</i>
</p>
<p id="first">
<b class="header">first</b><code>_.first(array, [n])</code>
<span class="alias">Aliases: <b>head</b>, <b>take</b></span>
<br />
Returns the first element of an <b>array</b>. Passing <b>n</b> will
return the first <b>n</b> elements of the array.
</p>
<pre>
_.first([5, 4, 3, 2, 1]);
=> 5
</pre>
<p id="initial">
<b class="header">initial</b><code>_.initial(array, [n])</code>
<br />
Returns everything but the last entry of the array. Especially useful on
the arguments object. Pass <b>n</b> to exclude the last <b>n</b> elements
from the result.
</p>
<pre>
_.initial([5, 4, 3, 2, 1]);
=> [5, 4, 3, 2]
</pre>
<p id="last">
<b class="header">last</b><code>_.last(array, [n])</code>
<br />
Returns the last element of an <b>array</b>. Passing <b>n</b> will return
the last <b>n</b> elements of the array.
</p>
<pre>
_.last([5, 4, 3, 2, 1]);
=> 1
</pre>
<p id="rest">
<b class="header">rest</b><code>_.rest(array, [index])</code>
<span class="alias">Aliases: <b>tail</b>, <b>drop</b></span>
<br />
Returns the <b>rest</b> of the elements in an array. Pass an <b>index</b>
to return the values of the array from that index onward.
</p>
<pre>
_.rest([5, 4, 3, 2, 1]);
=> [4, 3, 2, 1]
</pre>
<p id="flatten">
<b class="header">flatten</b><code>_.flatten(array, [shallow])</code>
<br />
Flattens a nested <b>array</b> (the nesting can be to any depth). If you
pass <b>shallow</b>, the array will only be flattened a single level.
</p>
<pre>
_.flatten([1, [2], [3, [[4]]]]);
=> [1, 2, 3, 4];
_.flatten([1, [2], [3, [[4]]]], true);
=> [1, 2, 3, [[4]]];
</pre>
<p id="without">
<b class="header">without</b><code>_.without(array, *values)</code>
<br />
Returns a copy of the <b>array</b> with all instances of the <b>values</b>
removed.
</p>
<pre>
_.without([1, 2, 1, 0, 3, 1, 4], 0, 1);
=> [2, 3, 4]
</pre>
<p id="union">
<b class="header">union</b><code>_.union(*arrays)</code>
<br />
Computes the union of the passed-in <b>arrays</b>: the list of unique items,
in order, that are present in one or more of the <b>arrays</b>.
</p>
<pre>
_.union([1, 2, 3], [101, 2, 1, 10], [2, 1]);
=> [1, 2, 3, 101, 10]
</pre>
<p id="intersection">
<b class="header">intersection</b><code>_.intersection(*arrays)</code>
<br />
Computes the list of values that are the intersection of all the <b>arrays</b>.
Each value in the result is present in each of the <b>arrays</b>.
</p>
<pre>
_.intersection([1, 2, 3], [101, 2, 1, 10], [2, 1]);
=> [1, 2]
</pre>
<p id="difference">
<b class="header">difference</b><code>_.difference(array, *others)</code>
<br />
Similar to <b>without</b>, but returns the values from <b>array</b> that
are not present in the <b>other</b> arrays.
</p>
<pre>
_.difference([1, 2, 3, 4, 5], [5, 2, 10]);
=> [1, 3, 4]
</pre>
<p id="uniq">
<b class="header">uniq</b><code>_.uniq(array, [isSorted], [iteratee])</code>
<span class="alias">Alias: <b>unique</b></span>
<br />
Produces a duplicate-free version of the <b>array</b>, using <i>===</i> to test
object equality. In particular only the first occurrence of each value is kept.
If you know in advance that the <b>array</b> is sorted,
passing <i>true</i> for <b>isSorted</b> will run a much faster algorithm.
If you want to compute unique items based on a transformation, pass an
<a href="#iteratee"><b>iteratee</b></a> function.