forked from jashkenas/underscore
-
Notifications
You must be signed in to change notification settings - Fork 0
/
Copy pathindex.html
1937 lines (1755 loc) · 68.5 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">
<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;
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;
font-family: Lucida Grande;
}
.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;
}
div.container {
width: 550px;
margin: 40px 0 50px 260px;
}
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;
}
ul {
list-style-type: circle;
padding: 0 0 0 20px;
}
li {
width: 500px;
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;
}
</style>
</head>
<body>
<div id="sidebar" class="interface">
<a class="toc_title" href="#">
Underscore.js <span class="version">(1.3.0)</span>
</a>
<a class="toc_title" href="#">
Introduction
</a>
<a class="toc_title" href="#collections">
Collections
</a>
<ul class="toc_section">
<li>- <a href="#each">each</a></li>
<li>- <a href="#map">map</a></li>
<li>- <a href="#reduce">reduce</a></li>
<li>- <a href="#reduceRight">reduceRight</a></li>
<li>- <a href="#find">find</a></li>
<li>- <a href="#filter">filter</a></li>
<li>- <a href="#reject">reject</a></li>
<li>- <a href="#all">all</a></li>
<li>- <a href="#any">any</a></li>
<li>- <a href="#include">include</a></li>
<li>- <a href="#invoke">invoke</a></li>
<li>- <a href="#pluck">pluck</a></li>
<li>- <a href="#max">max</a></li>
<li>- <a href="#min">min</a></li>
<li>- <a href="#sortBy">sortBy</a></li>
<li>- <a href="#groupBy">groupBy</a></li>
<li>- <a href="#sortedIndex">sortedIndex</a></li>
<li>- <a href="#shuffle">shuffle</a></li>
<li>- <a href="#toArray">toArray</a></li>
<li>- <a href="#size">size</a></li>
</ul>
<a class="toc_title" href="#arrays">
Arrays
</a>
<ul class="toc_section">
<li>- <a href="#first">first</a></li>
<li>- <a href="#initial">initial</a></li>
<li>- <a href="#last">last</a></li>
<li>- <a href="#rest">rest</a></li>
<li>- <a href="#compact">compact</a></li>
<li>- <a href="#flatten">flatten</a></li>
<li>- <a href="#without">without</a></li>
<li>- <a href="#union">union</a></li>
<li>- <a href="#intersection">intersection</a></li>
<li>- <a href="#difference">difference</a></li>
<li>- <a href="#uniq">uniq</a></li>
<li>- <a href="#zip">zip</a></li>
<li>- <a href="#indexOf">indexOf</a></li>
<li>- <a href="#lastIndexOf">lastIndexOf</a></li>
<li>- <a href="#range">range</a></li>
</ul>
<a class="toc_title" href="#functions">
Functions
</a>
<ul class="toc_section">
<li>- <a href="#bind">bind</a></li>
<li>- <a href="#bindAll">bindAll</a></li>
<li>- <a href="#memoize">memoize</a></li>
<li>- <a href="#delay">delay</a></li>
<li>- <a href="#defer">defer</a></li>
<li>- <a href="#throttle">throttle</a></li>
<li>- <a href="#debounce">debounce</a></li>
<li>- <a href="#once">once</a></li>
<li>- <a href="#after">after</a></li>
<li>- <a href="#wrap">wrap</a></li>
<li>- <a href="#compose">compose</a></li>
</ul>
<a class="toc_title" href="#objects">
Objects
</a>
<ul class="toc_section">
<li>- <a href="#keys">keys</a></li>
<li>- <a href="#values">values</a></li>
<li>- <a href="#functions">functions</a></li>
<li>- <a href="#extend">extend</a></li>
<li>- <a href="#defaults">defaults</a></li>
<li>- <a href="#clone">clone</a></li>
<li>- <a href="#tap">tap</a></li>
<li>- <a href="#isEqual">isEqual</a></li>
<li>- <a href="#isEmpty">isEmpty</a></li>
<li>- <a href="#isElement">isElement</a></li>
<li>- <a href="#isArray">isArray</a></li>
<li>- <a href="#isArguments">isArguments</a></li>
<li>- <a href="#isFunction">isFunction</a></li>
<li>- <a href="#isString">isString</a></li>
<li>- <a href="#isNumber">isNumber</a></li>
<li>- <a href="#isBoolean">isBoolean</a></li>
<li>- <a href="#isDate">isDate</a></li>
<li>- <a href="#isRegExp">isRegExp</a></li>
<li>- <a href="#isNaN">isNaN</a></li>
<li>- <a href="#isNull">isNull</a></li>
<li>- <a href="#isUndefined">isUndefined</a></li>
</ul>
<a class="toc_title" href="#utility">
Utility
</a>
<ul class="toc_section">
<li>- <a href="#noConflict">noConflict</a></li>
<li>- <a href="#identity">identity</a></li>
<li>- <a href="#times">times</a></li>
<li>- <a href="#mixin">mixin</a></li>
<li>- <a href="#uniqueId">uniqueId</a></li>
<li>- <a href="#escape">escape</a></li>
<li>- <a href="#template">template</a></li>
</ul>
<a class="toc_title" href="#chaining">
Chaining
</a>
<ul class="toc_section">
<li>- <a href="#chain">chain</a></li>
<li>- <a href="#value">value</a></li>
</ul>
<a class="toc_title" href="#links">
Links
</a>
<a class="toc_title" href="#changelog">
Change Log
</a>
</div>
<div class="container">
<p id="introduction">
<img style="width: 396px; height: 69px;" src="docs/images/underscore.png" alt="Underscore.js" />
</p>
<p>
<a href="http://github.com/documentcloud/underscore/">Underscore</a> is a
utility-belt library for JavaScript that provides a lot of the
functional programming support that you would expect in
<a href="http://prototypejs.org/api">Prototype.js</a>
(or <a href="http://www.ruby-doc.org/core/classes/Enumerable.html">Ruby</a>),
but without extending any of the built-in JavaScript objects. It's the
tie to go along with <a href="http://docs.jquery.com">jQuery</a>'s tux,
and <a href="http://backbonejs.org">Backbone.js</a>'s suspenders.
</p>
<p>
Underscore provides 60-odd functions that support both the usual
functional suspects: <b>map</b>, <b>select</b>, <b>invoke</b> —
as well as more specialized helpers: function binding, javascript
templating, deep equality testing, and so on. It delegates to built-in
functions, if present, so modern browsers will use the
native implementations of <b>forEach</b>, <b>map</b>, <b>reduce</b>,
<b>filter</b>, <b>every</b>, <b>some</b> and <b>indexOf</b>.
</p>
<p>
A complete <a href="test/test.html">Test & Benchmark 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>
The project is
<a href="http://github.com/documentcloud/underscore/">hosted on GitHub</a>.
You can report bugs and discuss features on the
<a href="http://github.com/documentcloud/underscore/issues">issues page</a>,
on Freenode in the <tt>#documentcloud</tt> channel,
or send tweets to <a href="http://twitter.com/documentcloud">@documentcloud</a>.
</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 (1.3.0)</a></td>
<td><i>34kb, Uncompressed with Comments</i></td>
</tr>
<tr>
<td><a href="underscore-min.js">Production Version (1.3.0)</a></td>
<td><i>< 4kb, Minified and Gzipped</i></td>
</tr>
</table>
<div class="warning">Upgrade warning: version 1.3.0 removes AMD (RequireJS) support.</div>
<div id="documentation">
<h2 id="collections">Collection Functions (Arrays or Objects)</h2>
<p id="each">
<b class="header">each</b><code>_.each(list, iterator, [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>iterator</b>
function. The <b>iterator</b> is bound to the <b>context</b> object, if one is
passed. Each invocation of <b>iterator</b> is called with three arguments:
<tt>(element, index, list)</tt>. If <b>list</b> is a JavaScript object, <b>iterator</b>'s
arguments will be <tt>(value, key, list)</tt>. Delegates to the native
<b>forEach</b> function if it exists.
</p>
<pre>
_.each([1, 2, 3], function(num){ alert(num); });
=> alerts each number in turn...
_.each({one : 1, two : 2, three : 3}, function(num, key){ alert(num); });
=> alerts each number in turn...</pre>
<p id="map">
<b class="header">map</b><code>_.map(list, iterator, [context])</code>
<br />
Produces a new array of values by mapping each value in <b>list</b>
through a transformation function (<b>iterator</b>). If the native <b>map</b> method
exists, it will be used instead. If <b>list</b> is a JavaScript object,
<b>iterator</b>'s arguments will be <tt>(value, key, 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]</pre>
<p id="reduce">
<b class="header">reduce</b><code>_.reduce(list, iterator, memo, [context])</code>
<span class="alias">Aliases: <b>inject, foldl</b></span>
<br />
Also known as <b>inject</b> and <b>foldl</b>, <b>reduce</b> 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>iterator</b>.
</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, iterator, memo, [context])</code>
<span class="alias">Alias: <b>foldr</b></span>
<br />
The right-associative version of <b>reduce</b>. Delegates to the
JavaScript 1.8 version of <b>reduceRight</b>, if it exists. <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, iterator, [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>iterator</b>). The function returns as
soon as it finds an acceptable element, and doesn't traverse the
entire list.
</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, iterator, [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>iterator</b>). Delegates to the
native <b>filter</b> method, if it exists.
</p>
<pre>
var evens = _.filter([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; });
=> [2, 4, 6]
</pre>
<p id="reject">
<b class="header">reject</b><code>_.reject(list, iterator, [context])</code>
<br />
Returns the values in <b>list</b> without the elements that the truth
test (<b>iterator</b>) passes. The opposite of <b>filter</b>.
</p>
<pre>
var odds = _.reject([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; });
=> [1, 3, 5]
</pre>
<p id="all">
<b class="header">all</b><code>_.all(list, iterator, [context])</code>
<span class="alias">Alias: <b>every</b></span>
<br />
Returns <i>true</i> if all of the values in the <b>list</b> pass the <b>iterator</b>
truth test. Delegates to the native method <b>every</b>, if present.
</p>
<pre>
_.all([true, 1, null, 'yes'], _.identity);
=> false
</pre>
<p id="any">
<b class="header">any</b><code>_.any(list, [iterator], [context])</code>
<span class="alias">Alias: <b>some</b></span>
<br />
Returns <i>true</i> if any of the values in the <b>list</b> pass the
<b>iterator</b> truth test. Short-circuits and stops traversing the list
if a true element is found. Delegates to the native method <b>some</b>,
if present.
</p>
<pre>
_.any([null, 0, 'yes', false]);
=> true
</pre>
<p id="include">
<b class="header">include</b><code>_.include(list, value)</code>
<span class="alias">Alias: <b>contains</b></span>
<br />
Returns <i>true</i> if the <b>value</b> is present in the <b>list</b>, using
<i>===</i> to test equality. Uses <b>indexOf</b> internally, if <b>list</b>
is an Array.
</p>
<pre>
_.include([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, [iterator], [context])</code>
<br />
Returns the maximum value in <b>list</b>. If <b>iterator</b> is passed,
it will be used on each value to generate the criterion by which the
value is ranked.
</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, [iterator], [context])</code>
<br />
Returns the minimum value in <b>list</b>. If <b>iterator</b> is passed,
it will be used on each value to generate the criterion by which the
value is ranked.
</p>
<pre>
var numbers = [10, 5, 100, 2, 1000];
_.min(numbers);
=> 2
</pre>
<p id="sortBy">
<b class="header">sortBy</b><code>_.sortBy(list, iterator, [context])</code>
<br />
Returns a sorted copy of <b>list</b>, ranked by the results of running
each value through <b>iterator</b>.
</p>
<pre>
_.sortBy([1, 2, 3, 4, 5, 6], function(num){ return Math.sin(num); });
=> [5, 4, 6, 3, 1, 2]
</pre>
<p id="groupBy">
<b class="header">groupBy</b><code>_.groupBy(list, iterator)</code>
<br />
Splits a collection into sets, grouped by the result of running each
value through <b>iterator</b>. If <b>iterator</b> is a string instead of
a function, groups by the property named by <b>iterator</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="sortedIndex">
<b class="header">sortedIndex</b><code>_.sortedIndex(list, value, [iterator])</code>
<br />
Uses a binary search to determine the index at which the <b>value</b>
<i>should</i> be inserted into the <b>list</b> in order to maintain the <b>list</b>'s
sorted order. If an <b>iterator</b> is passed, it will be used to compute
the sort ranking of each value.
</p>
<pre>
_.sortedIndex([10, 20, 30, 40, 50], 35);
=> 3
</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="toArray">
<b class="header">toArray</b><code>_.toArray(list)</code>
<br />
Converts the <b>list</b> (anything that can be iterated over), into a
real Array. Useful for transmuting the <b>arguments</b> object.
</p>
<pre>
(function(){ return _.toArray(arguments).slice(0); })(1, 2, 3);
=> [1, 2, 3]
</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({one : 1, two : 2, three : 3});
=> 3
</pre>
<h2 id="arrays">Array Functions</h2>
<p>
<i>Note: All array functions will also work on the <b>arguments</b> object.</i>
</p>
<p id="first">
<b class="header">first</b><code>_.first(array, [n])</code>
<span class="alias">Alias: <b>head</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">Alias: <b>tail</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="compact">
<b class="header">compact</b><code>_.compact(array)</code>
<br />
Returns a copy of the <b>array</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>
<p id="flatten">
<b class="header">flatten</b><code>_.flatten(array)</code>
<br />
Flattens a nested <b>array</b> (the nesting can be to any depth).
</p>
<pre>
_.flatten([1, [2], [3, [[[4]]]]]);
=> [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. <i>===</i> is used for the equality test.
</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], [iterator])</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. 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
<b>iterator</b> function.
</p>
<pre>
_.uniq([1, 2, 1, 3, 1, 4]);
=> [1, 2, 3, 4]
</pre>
<p id="zip">
<b class="header">zip</b><code>_.zip(*arrays)</code>
<br />
Merges together the values of each of the <b>arrays</b> with the
values at the corresponding position. Useful when you have separate
data sources that are coordinated through matching array indexes.
If you're working with a matrix of nested arrays, <b>zip.apply</b>
can transpose the matrix in a similar fashion.
</p>
<pre>
_.zip(['moe', 'larry', 'curly'], [30, 40, 50], [true, false, false]);
=> [["moe", 30, true], ["larry", 40, false], ["curly", 50, false]]
</pre>
<p id="indexOf">
<b class="header">indexOf</b><code>_.indexOf(array, value, [isSorted])</code>
<br />
Returns the index at which <b>value</b> can be found in the <b>array</b>,
or <i>-1</i> if value is not present in the <b>array</b>. Uses the native
<b>indexOf</b> function unless it's missing. If you're working with a
large array, and you know that the array is already sorted, pass <tt>true</tt>
for <b>isSorted</b> to use a faster binary search.
</p>
<pre>
_.indexOf([1, 2, 3], 2);
=> 1
</pre>
<p id="lastIndexOf">
<b class="header">lastIndexOf</b><code>_.lastIndexOf(array, value)</code>
<br />
Returns the index of the last occurrence of <b>value</b> in the <b>array</b>,
or <i>-1</i> if value is not present. Uses the native <b>lastIndexOf</b>
function if possible.
</p>
<pre>
_.lastIndexOf([1, 2, 3, 1, 2, 3], 2);
=> 4
</pre>
<p id="range">
<b class="header">range</b><code>_.range([start], stop, [step])</code>
<br />
A function to create flexibly-numbered lists of integers, handy for
<tt>each</tt> and <tt>map</tt> loops. <b>start</b>, if omitted, defaults
to <i>0</i>; <b>step</b> defaults to <i>1</i>. Returns a list of integers
from <b>start</b> to <b>stop</b>, incremented (or decremented) by <b>step</b>,
exclusive.
</p>
<pre>
_.range(10);
=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
_.range(1, 11);
=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
_.range(0, 30, 5);
=> [0, 5, 10, 15, 20, 25]
_.range(0, -10, -1);
=> [0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
_.range(0);
=> []
</pre>
<h2 id="functions">Function (uh, ahem) Functions</h2>
<p id="bind">
<b class="header">bind</b><code>_.bind(function, object, [*arguments])</code>
<br />
Bind a <b>function</b> to an <b>object</b>, meaning that whenever
the function is called, the value of <i>this</i> will be the <b>object</b>.
Optionally, bind <b>arguments</b> to the <b>function</b> to pre-fill them,
also known as <b>partial application</b>.
</p>
<pre>
var func = function(greeting){ return greeting + ': ' + this.name };
func = _.bind(func, {name : 'moe'}, 'hi');
func();
=> 'hi: moe'
</pre>
<p id="bindAll">
<b class="header">bindAll</b><code>_.bindAll(object, [*methodNames])</code>
<br />
Binds a number of methods on the <b>object</b>, specified by
<b>methodNames</b>, to be run in the context of that object whenever they
are invoked. Very handy for binding functions that are going to be used
as event handlers, which would otherwise be invoked with a fairly useless
<i>this</i>. If no <b>methodNames</b> are provided, all of the object's
function properties will be bound to it.
</p>
<pre>
var buttonView = {
label : 'underscore',
onClick : function(){ alert('clicked: ' + this.label); },
onHover : function(){ console.log('hovering: ' + this.label); }
};
_.bindAll(buttonView);
jQuery('#underscore_button').bind('click', buttonView.onClick);
=> When the button is clicked, this.label will have the correct value...
</pre>
<p id="memoize">
<b class="header">memoize</b><code>_.memoize(function, [hashFunction])</code>
<br />
Memoizes a given <b>function</b> by caching the computed result. Useful
for speeding up slow-running computations. If passed an optional
<b>hashFunction</b>, it will be used to compute the hash key for storing
the result, based on the arguments to the original function. The default
<b>hashFunction</b> just uses the first argument to the memoized function
as the key.
</p>
<pre>
var fibonacci = _.memoize(function(n) {
return n < 2 ? n : fibonacci(n - 1) + fibonacci(n - 2);
});
</pre>
<p id="delay">
<b class="header">delay</b><code>_.delay(function, wait, [*arguments])</code>
<br />
Much like <b>setTimeout</b>, invokes <b>function</b> after <b>wait</b>
milliseconds. If you pass the optional <b>arguments</b>, they will be
forwarded on to the <b>function</b> when it is invoked.
</p>
<pre>
var log = _.bind(console.log, console);
_.delay(log, 1000, 'logged later');
=> 'logged later' // Appears after one second.
</pre>
<p id="defer">
<b class="header">defer</b><code>_.defer(function)</code>
<br />
Defers invoking the <b>function</b> until the current call stack has cleared,
similar to using <b>setTimeout</b> with a delay of 0. Useful for performing
expensive computations or HTML rendering in chunks without blocking the UI thread
from updating.
</p>
<pre>
_.defer(function(){ alert('deferred'); });
// Returns from the function before the alert runs.
</pre>
<p id="throttle">
<b class="header">throttle</b><code>_.throttle(function, wait)</code>
<br />
Creates and returns a new, throttled version of the passed function,
that, when invoked repeatedly, will only actually call the original function
at most once per every <b>wait</b>
milliseconds. Useful for rate-limiting events that occur faster than you
can keep up with.
</p>
<pre>
var throttled = _.throttle(updatePosition, 100);
$(window).scroll(throttled);
</pre>
<p id="debounce">
<b class="header">debounce</b><code>_.debounce(function, wait)</code>
<br />
Creates and returns a new debounced version of the passed function that
will postpone its execution until after
<b>wait</b> milliseconds have elapsed since the last time it
was invoked. Useful for implementing behavior that should only happen
<i>after</i> the input has stopped arriving. For example: rendering a
preview of a Markdown comment, recalculating a layout after the window
has stopped being resized, and so on.
</p>
<pre>
var lazyLayout = _.debounce(calculateLayout, 300);
$(window).resize(lazyLayout);
</pre>
<p id="once">
<b class="header">once</b><code>_.once(function)</code>
<br />
Creates a version of the function that can only be called one time.
Repeated calls to the modified function will have no effect, returning
the value from the original call. Useful for initialization functions,
instead of having to set a boolean flag and then check it later.
</p>
<pre>
var initialize = _.once(createApplication);
initialize();
initialize();
// Application is only created once.
</pre>
<p id="after">
<b class="header">after</b><code>_.after(count, function)</code>
<br />
Creates a version of the function that will only be run after first
being called <b>count</b> times. Useful for grouping asynchronous responses,
where you want to be sure that all the async calls have finished, before
proceeding.
</p>
<pre>
var renderNotes = _.after(notes.length, render);
_.each(notes, function(note) {
note.asyncSave({success: renderNotes});
});
// renderNotes is run once, after all notes have saved.
</pre>
<p id="wrap">
<b class="header">wrap</b><code>_.wrap(function, wrapper)</code>
<br />
Wraps the first <b>function</b> inside of the <b>wrapper</b> function,
passing it as the first argument. This allows the <b>wrapper</b> to
execute code before and after the <b>function</b> runs, adjust the arguments,
and execute it conditionally.
</p>
<pre>
var hello = function(name) { return "hello: " + name; };
hello = _.wrap(hello, function(func) {
return "before, " + func("moe") + ", after";
});
hello();
=> 'before, hello: moe, after'
</pre>
<p id="compose">
<b class="header">compose</b><code>_.compose(*functions)</code>
<br />
Returns the composition of a list of <b>functions</b>, where each function
consumes the return value of the function that follows. In math terms,
composing the functions <i>f()</i>, <i>g()</i>, and <i>h()</i> produces
<i>f(g(h()))</i>.
</p>
<pre>
var greet = function(name){ return "hi: " + name; };
var exclaim = function(statement){ return statement + "!"; };
var welcome = _.compose(exclaim, greet);
welcome('moe');
=> 'hi: moe!'
</pre>
<h2 id="objects">Object Functions</h2>
<p id="keys">
<b class="header">keys</b><code>_.keys(object)</code>
<br />
Retrieve all the names of the <b>object</b>'s properties.
</p>
<pre>
_.keys({one : 1, two : 2, three : 3});
=> ["one", "two", "three"]
</pre>
<p id="values">
<b class="header">values</b><code>_.values(object)</code>
<br />
Return all of the values of the <b>object</b>'s properties.
</p>
<pre>
_.values({one : 1, two : 2, three : 3});
=> [1, 2, 3]
</pre>
<p id="functions">
<b class="header">functions</b><code>_.functions(object)</code>
<span class="alias">Alias: <b>methods</b></span>
<br />
Returns a sorted list of the names of every method in an object —
that is to say, the name of every function property of the object.
</p>
<pre>
_.functions(_);
=> ["all", "any", "bind", "bindAll", "clone", "compact", "compose" ...
</pre>
<p id="extend">
<b class="header">extend</b><code>_.extend(destination, *sources)</code>
<br />
Copy all of the properties in the <b>source</b> objects over to the