forked from w3c/csswg-drafts
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathOverview.html
More file actions
3771 lines (3121 loc) · 240 KB
/
Copy pathOverview.html
File metadata and controls
3771 lines (3121 loc) · 240 KB
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 lang=en><head>
<meta content="text/html; charset=utf-8" http-equiv=Content-Type>
<title>Selectors Level 4</title>
<link href=../default.css rel=stylesheet type=text/css>
<link href=../csslogo.ico rel="shortcut icon" type=image/x-icon>
<style>
body {
background: url("https://www.w3.org/StyleSheets/TR/logo-ED") top left no-repeat white;
background-attachment: fixed;
color: black;
font-family: sans-serif;
margin: 0 auto;
max-width: 50em;
padding: 2em 1em 2em 70px;
}
:link { color: #00C; background: transparent }
:visited { color: #609; background: transparent }
a[href]:active { color: #C00; background: transparent }
a[href]:hover { background: #ffa }
a[href] img { border-style: none }
h1, h2, h3, h4, h5, h6 { text-align: left }
h1, h2, h3 { color: #005A9C; }
h1 { font: 170% sans-serif }
h2 { font: 140% sans-serif }
h3 { font: 120% sans-serif }
h4 { font: bold 100% sans-serif }
h5 { font: italic 100% sans-serif }
h6 { font: small-caps 100% sans-serif }
.hide { display: none }
div.head { margin-bottom: 1em }
div.head h1 { margin-top: 2em; clear: both }
div.head table { margin-left: 2em; margin-top: 2em }
p.copyright { font-size: small }
p.copyright small { font-size: small }
pre { margin-left: 2em }
dt { font-weight: bold }
ul.toc, ol.toc {
list-style: none;
}
</style>
<style>
.tprofile td, th { vertical-align: baseline; padding: 0 0.5em; }
.tprofile th { text-align: right; }
</style>
</head>
<body class=h-entry>
<div class=head>
<p data-fill-with=logo><a class=logo href=http://www.w3.org/>
<img alt=W3C height=48 src=http://www.w3.org/Icons/w3c_home width=72>
</a>
</p>
<h1 class="p-name no-ref" id=title>Selectors Level 4</h1>
<h2 class="no-num no-toc no-ref heading settled heading" id=subtitle><span class=content>Editor’s Draft,
<span class=dt-updated><span class=value-title title=20140418>18 April 2014</span></span></span></h2>
<div data-fill-with=spec-metadata><dl><dt>This version:<dd><a class=u-url href=http://dev.w3.org/csswg/selectors>http://dev.w3.org/csswg/selectors</a><dt>Latest version:<dd><a href=http://www.w3.org/TR/selectors/>http://www.w3.org/TR/selectors/</a><dt>Editor’s Draft:<dd><a href=http://dev.w3.org/csswg/selectors>http://dev.w3.org/csswg/selectors</a><dt>Previous Versions:<dd><a href=http://www.w3.org/TR/2013/WD-selectors4-20130502/ rel=previous>http://www.w3.org/TR/2013/WD-selectors4-20130502/</a><dd><a href=http://www.w3.org/TR/2012/WD-selectors4-20120823/ rel=previous>http://www.w3.org/TR/2012/WD-selectors4-20120823/</a><dd><a href=http://www.w3.org/TR/2011/WD-selectors4-20110929/ rel=previous>http://www.w3.org/TR/2011/WD-selectors4-20110929/</a>
<dt>Feedback:</dt>
<dd><a href="mailto:www-style@w3.org?subject=%5Bselectors%5D%20feedback">www-style@w3.org</a>
with subject line
“<kbd>[selectors] <var>… message topic …</var></kbd>”(<a href=http://lists.w3.org/Archives/Public/www-style/ rel=discussion>archives</a>)<dt>Test Suite:<dd>None Yet<dt>Editors:
<dd class="p-author h-card vcard"><a class="p-name fn u-url url" href=http://fantasai.inkedblade.net/contact>Elika J. Etemad</a> (<span class="p-org org">Invited Expert</span>)<dd class="p-author h-card vcard"><a class="p-name fn u-url url" href=http://xanthir.com/contact/>Tab Atkins Jr.</a> (<span class="p-org org">Google</span>)<dt>Former Editors:
<dd class="p-author h-card vcard"><a class="p-name fn u-url url" href=http://www.tantek.com>Tantek Çelik</a><dd class="p-author h-card vcard"><span class="p-name fn">Daniel Glazman</span><dd class="p-author h-card vcard"><span class="p-name fn">Ian Hickson</span><dd class="p-author h-card vcard"><span class="p-name fn">Peter Linss</span><dd class="p-author h-card vcard"><span class="p-name fn">John Williams</span></dl></div>
<div data-fill-with=warning></div>
<p class=copyright data-fill-with=copyright><a href=http://www.w3.org/Consortium/Legal/ipr-notice#Copyright>Copyright</a> © 2014 <a href=http://www.w3.org/><abbr title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> (<a href=http://www.csail.mit.edu/><abbr title="Massachusetts Institute of Technology">MIT</abbr></a>, <a href=http://www.ercim.eu/><abbr title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href=http://www.keio.ac.jp/>Keio</a>, <a href=http://ev.buaa.edu.cn/>Beihang</a>), All Rights Reserved. W3C <a href=http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer>liability</a>, <a href=http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks>trademark</a> and <a href=http://www.w3.org/Consortium/Legal/copyright-documents>document use</a> rules apply.
</p>
<hr title="Separator for header">
</div>
<h2 class="no-num no-toc no-ref heading settled heading" id=abstract><span class=content>Abstract</span></h2>
<p class=p-summary data-fill-with=abstract><b>Selectors</b> are patterns that match against elements in a tree, and as such form one of several technologies that can be used to select nodes in a document. Selectors have been optimized for use with HTML and XML, and are designed to be usable in performance-critical code. They are a core component of <abbr title="Cascading Style Sheets">CSS</abbr> (Cascading Style Sheets), which uses Selectors to bind style properties to elements in the document.<p>Selectors Level 4 describes the selectors that already exist in <a data-biblio-type=normative data-link-type=biblio href=#select title=select>[SELECT]</a>, and further introduces new selectors for CSS and other languages that may need them.
<a href=http://www.w3.org/TR/CSS/>CSS</a> is a language for describing the rendering of structured documents
(such as HTML and XML)
on screen, on paper, in speech, etc.</p>
<h2 class="no-num no-toc no-ref heading settled heading" id=status><span class=content>Status of this document</span></h2>
<div data-fill-with=status><p>
This is a public copy of the editors’ draft.
It is provided for discussion only and may change at any moment.
Its publication here does not imply endorsement of its contents by W3C.
Don’t cite this document other than as work in progress.
<p>
The (<a href=http://lists.w3.org/Archives/Public/www-style/>archived</a>) public mailing list
<a href="mailto:www-style@w3.org?Subject=%5Bselectors%5D%20PUT%20SUBJECT%20HERE">www-style@w3.org</a>
(see <a href=http://www.w3.org/Mail/Request>instructions</a>)
is preferred for discussion of this specification.
When sending e-mail,
please put the text “selectors” in the subject,
preferably like this:
“[selectors] <em>…summary of comment…</em>”
<p>
This document was produced by the <a href=http://www.w3.org/Style/CSS/members>CSS Working Group</a>
(part of the <a href=http://www.w3.org/Style/>Style Activity</a>).
<p>
This document was produced by a group operating under
the <a href=http://www.w3.org/Consortium/Patent-Policy-20040205/>5 February 2004 W3C Patent Policy</a>.
W3C maintains a <a href=http://www.w3.org/2004/01/pp-impl/32061/status rel=disclosure>public list of any patent disclosures</a>
made in connection with the deliverables of the group;
that page also includes instructions for disclosing a patent.
An individual who has actual knowledge of a patent which the individual believes contains <a href=http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential>Essential Claim(s)</a>
must disclose the information in accordance with <a href=http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure>section 6 of the W3C Patent Policy</a>.</div>
<div data-fill-with=at-risk><p>The following features are at-risk, and may be dropped during the CR period:
<ul><li>the column combinator<li>The <a class=css data-link-type=maybe href=#selectordef-drop title=:drop()>:drop()</a> pseudo-class</ul></div>
<h2 class="no-num no-toc no-ref heading settled heading" id=contents><span class=content>Table of Contents</span></h2>
<div data-fill-with=table-of-contents><ul class=toc>
<li><a href=#context><span class=secno>1</span> Introduction</a>
<ul class=toc>
<li><a href=#placement><span class=secno>1.1</span>Module Interactions</a></ul>
<li><a href=#overview><span class=secno>2</span> Selectors Overview</a>
<ul class=toc>
<li><a href=#profiles><span class=secno>2.1</span> <span data-link-type=dfn title=fast>Fast</span> vs <span data-link-type=dfn title=complete>Complete</span> Selector Profiles</a></ul>
<li><a href=#syntax><span class=secno>3</span> Selector Syntax and Structure</a>
<ul class=toc>
<li><a href=#structure><span class=secno>3.1</span> Structure and Terminology</a>
<li><a href=#evaluating-selectors><span class=secno>3.2</span> Evaluating a Selector</a>
<li><a href=#data-model><span class=secno>3.3</span> Data Model</a>
<li><a href=#scoping><span class=secno>3.4</span> Scoped Selectors</a>
<li><a href=#relative><span class=secno>3.5</span> Relative Selectors</a>
<ul class=toc>
<li><a href=#absolutizing><span class=secno>3.5.1</span> Absolutizing a Relative Selector</a></ul>
<li><a href=#pseudo-classes><span class=secno>3.6</span> Pseudo-classes</a>
<li><a href=#pseudo-elements><span class=secno>3.7</span>Pseudo-elements</a>
<ul class=toc>
<li><a href=#pseudo-element-types><span class=secno>3.7.1</span> Types of Pseudo-Elements</a></ul>
<li><a href=#case-sensitive><span class=secno>3.8</span> Characters and case sensitivity</a>
<li><a href=#namespaces><span class=secno>3.9</span> Namespaces</a>
<li><a href=#invalid><span class=secno>3.10</span> Invalid Selectors and Error Handling</a></ul>
<li><a href=#logical-combination><span class=secno>4</span> Logical Combinations</a>
<ul class=toc>
<li><a href=#grouping><span class=secno>4.1</span> Selector Lists</a>
<li><a href=#matches><span class=secno>4.2</span> The Matches-Any Pseudo-class: <span class=css data-link-type=maybe title=:matches()>:matches()</span></a>
<li><a href=#negation><span class=secno>4.3</span> The Negation Pseudo-class: <span class=css data-link-type=maybe title=:not()>:not()</span></a></ul>
<li><a href=#elemental-selectors><span class=secno>5</span> Elemental selectors</a>
<ul class=toc>
<li><a href=#type-selectors><span class=secno>5.1</span> Type (tag name) selector</a>
<ul class=toc>
<li><a href=#typenmsp><span class=secno>5.1.1</span> Type selectors and namespaces</a></ul>
<li><a href=#universal-selector><span class=secno>5.2</span> Universal selector </a>
<ul class=toc>
<li><a href=#univnmsp><span class=secno>5.2.1</span> Universal selector and namespaces</a></ul></ul>
<li><a href=#attribute-selectors><span class=secno>6</span> Attribute selectors</a>
<ul class=toc>
<li><a href=#attribute-representation><span class=secno>6.1</span> Attribute presence and value selectors</a>
<li><a href=#attribute-substrings><span class=secno>6.2</span> Substring matching attribute selectors</a>
<li><a href=#attribute-case><span class=secno>6.3</span> Case-sensitivity</a>
<li><a href=#attrnmsp><span class=secno>6.4</span> Attribute selectors and namespaces</a>
<li><a href=#def-values><span class=secno>6.5</span> Default attribute values in DTDs</a>
<li><a href=#class-html><span class=secno>6.6</span> Class selectors</a>
<li><a href=#id-selectors><span class=secno>6.7</span> ID selectors</a></ul>
<li><a href=#linguistic-pseudos><span class=secno>7</span> Linguistic Pseudo-classes</a>
<ul class=toc>
<li><a href=#the-dir-pseudo><span class=secno>7.1</span> The directionality pseudo-class <span class=css data-link-type=maybe title=:dir()>:dir()</span></a>
<li><a href=#the-lang-pseudo><span class=secno>7.2</span> The language pseudo-class <span class=css data-link-type=maybe title=:lang()>:lang()</span></a></ul>
<li><a href=#location><span class=secno>8</span> Location Pseudo-classes</a>
<ul class=toc>
<li><a href=#the-any-link-pseudo><span class=secno>8.1</span> The hyperlink pseudo-class: <span class=css data-link-type=maybe title=:any-link>:any-link</span></a>
<li><a href=#link><span class=secno>8.2</span> The link history pseudo-classes: <span class=css data-link-type=maybe title=:link>:link</span> and <span class=css data-link-type=maybe title=:visited>:visited</span></a>
<li><a href=#local-pseudo><span class=secno>8.3</span> The local link pseudo-class <span class=css data-link-type=maybe title=:local-link>:local-link</span></a>
<li><a href=#the-target-pseudo><span class=secno>8.4</span> The target pseudo-class <span class=css data-link-type=maybe title=:target>:target</span></a>
<li><a href=#the-scope-pseudo><span class=secno>8.5</span> The reference element pseudo-class <span class=css data-link-type=maybe title=:scope>:scope</span></a></ul>
<li><a href=#useraction-pseudos><span class=secno>9</span> User Action Pseudo-classes</a>
<ul class=toc>
<li><a href=#the-hover-pseudo><span class=secno>9.1</span> The pointer hover pseudo-class <span class=css data-link-type=maybe title=:hover>:hover</span></a>
<li><a href=#the-active-pseudo><span class=secno>9.2</span> The activation pseudo-class <span class=css data-link-type=maybe title=:active>:active</span></a>
<li><a href=#the-focus-pseudo><span class=secno>9.3</span> The input focus pseudo-class <span class=css data-link-type=maybe title=:focus>:focus</span></a>
<li><a href=#drag-pseudos><span class=secno>9.4</span> The drag-and-drop pseudo-class <span class=css data-link-type=maybe title=:drop>:drop</span> and <span class=css data-link-type=maybe title=:drop()>:drop()</span></a></ul>
<li><a href=#time-pseudos><span class=secno>10</span> Time-dimensional Pseudo-classes</a>
<ul class=toc>
<li><a href=#the-current-pseudo><span class=secno>10.1</span> The current-element pseudo-class <span class=css data-link-type=maybe title=:current>:current</span></a>
<li><a href=#the-past-pseudo><span class=secno>10.2</span> The past-element pseudo-class <span class=css data-link-type=maybe title=:past>:past</span></a>
<li><a href=#the-future-pseudo><span class=secno>10.3</span> The future-element pseudo-class <span class=css data-link-type=maybe title=:future>:future</span></a></ul>
<li><a href=#input-pseudos><span class=secno>11</span> The Input Pseudo-classes</a>
<ul class=toc>
<li><a href=#input-states><span class=secno>11.1</span> Input Control States</a>
<ul class=toc>
<li><a href=#enableddisabled><span class=secno>11.1.1</span> The <span class=css data-link-type=maybe title=:enabled>:enabled</span> and <span class=css data-link-type=maybe title=:disabled>:disabled</span> pseudo-classes</a>
<li><a href=#rw-pseudos><span class=secno>11.1.2</span> The mutability pseudo-classes <span class=css data-link-type=maybe title=:read-only>:read-only</span> and <span class=css data-link-type=maybe title=:read-write>:read-write</span></a>
<li><a href=#placeholder><span class=secno>11.1.3</span> The placeholder-shown pseudo-class <span class=css data-link-type=maybe title=:placeholder-shown>:placeholder-shown</span></a>
<li><a href=#the-default-pseudo><span class=secno>11.1.4</span> The default-option pseudo-class <span class=css data-link-type=maybe title=:default>:default</span></a></ul>
<li><a href=#input-value-states><span class=secno>11.2</span> Input Value States</a>
<ul class=toc>
<li><a href=#checked><span class=secno>11.2.1</span> The selected-option pseudo-class <span class=css data-link-type=maybe title=:checked>:checked</span></a>
<li><a href=#indeterminate><span class=secno>11.2.2</span> The indeterminate-value pseudo-class <span class=css data-link-type=maybe title=:indeterminate>:indeterminate</span></a></ul>
<li><a href=#ui-validity><span class=secno>11.3</span> Input Value-checking</a>
<ul class=toc>
<li><a href=#validity-pseudos><span class=secno>11.3.1</span> The validity pseudo-classes: <span class=css data-link-type=maybe title=:valid>:valid</span> and <span class=css data-link-type=maybe title=:invalid>:invalid</span></a>
<li><a href=#range-pseudos><span class=secno>11.3.2</span> The range pseudo-classes <span class=css data-link-type=maybe title=:in-range>:in-range</span> and <span class=css data-link-type=maybe title=:out-of-range>:out-of-range</span></a>
<li><a href=#opt-pseudos><span class=secno>11.3.3</span> The optionality pseudo-classes <span class=css data-link-type=maybe title=:required>:required</span> and <span class=css data-link-type=maybe title=:optional>:optional</span></a>
<li><a href=#user-pseudos><span class=secno>11.3.4</span> The user-interaction pseudo-class <span class=css data-link-type=maybe title=:user-error>:user-error</span></a></ul></ul>
<li><a href=#structural-pseudos><span class=secno>12</span> Tree-Structural pseudo-classes</a>
<ul class=toc>
<li><a href=#the-root-pseudo><span class=secno>12.1</span> <span class=css data-link-type=maybe title=:root>:root</span> pseudo-class</a>
<li><a href=#the-empty-pseudo><span class=secno>12.2</span> <span class=css data-link-type=maybe title=:empty>:empty</span> pseudo-class</a>
<li><a href=#the-blank-pseudo><span class=secno>12.3</span> <span class=css data-link-type=maybe title=:blank>:blank</span> pseudo-class</a>
<li><a href=#child-index><span class=secno>12.4</span> Child-indexed Pseudo-classes</a>
<ul class=toc>
<li><a href=#the-nth-child-pseudo><span class=secno>12.4.1</span> <span class=css data-link-type=maybe title=:nth-child()>:nth-child()</span> pseudo-class</a>
<li><a href=#the-nth-last-child-pseudo><span class=secno>12.4.2</span> <span class=css data-link-type=maybe title=:nth-last-child()>:nth-last-child()</span> pseudo-class</a>
<li><a href=#the-first-child-pseudo><span class=secno>12.4.3</span> <span class=css data-link-type=maybe title=:first-child>:first-child</span> pseudo-class</a>
<li><a href=#the-last-child-pseudo><span class=secno>12.4.4</span> <span class=css data-link-type=maybe title=:last-child>:last-child</span> pseudo-class</a>
<li><a href=#the-only-child-pseudo><span class=secno>12.4.5</span> <span class=css data-link-type=maybe title=:only-child>:only-child</span> pseudo-class</a></ul>
<li><a href=#typed-child-index><span class=secno>12.5</span> Typed Child-indexed Pseudo-classes</a>
<ul class=toc>
<li><a href=#the-nth-of-type-pseudo><span class=secno>12.5.1</span> <span class=css data-link-type=maybe title=:nth-of-type()>:nth-of-type()</span> pseudo-class</a>
<li><a href=#the-nth-last-of-type-pseudo><span class=secno>12.5.2</span> <span class=css data-link-type=maybe title=:nth-last-of-type()>:nth-last-of-type()</span> pseudo-class</a>
<li><a href=#the-first-of-type-pseudo><span class=secno>12.5.3</span> <span class=css data-link-type=maybe title=:first-of-type>:first-of-type</span> pseudo-class</a>
<li><a href=#the-last-of-type-pseudo><span class=secno>12.5.4</span> <span class=css data-link-type=maybe title=:last-of-type>:last-of-type</span> pseudo-class</a>
<li><a href=#the-only-of-type-pseudo><span class=secno>12.5.5</span> <span class=css data-link-type=maybe title=:only-of-type>:only-of-type</span> pseudo-class</a></ul>
<li><a href=#selected-child-index><span class=secno>12.6</span> Selected Child-indexed Pseudo-classes</a>
<ul class=toc>
<li><a href=#the-nth-match-pseudo><span class=secno>12.6.1</span> <span class=css data-link-type=maybe title=:nth-match()>:nth-match()</span> pseudo-class</a>
<li><a href=#the-nth-last-match-pseudo><span class=secno>12.6.2</span> <span class=css data-link-type=maybe title=:nth-last-match()>:nth-last-match()</span> pseudo-class</a></ul></ul>
<li><a href=#combinators><span class=secno>13</span> Combinators</a>
<ul class=toc>
<li><a href=#descendant-combinators><span class=secno>13.1</span> Descendant combinator (<code> </code>)</a>
<li><a href=#child-combinators><span class=secno>13.2</span> Child combinator (<code>></code>)</a>
<li><a href=#adjacent-sibling-combinators><span class=secno>13.3</span> Next-sibling combinator (<code>+</code>)</a>
<li><a href=#general-sibling-combinators><span class=secno>13.4</span> Following-sibling combinator (<code>~</code>)</a>
<li><a href=#idref-combinators><span class=secno>13.5</span> Reference combinators <code>/ref/</code></a></ul>
<li><a href=#table-pseudos><span class=secno>14</span> Grid-Structural Selectors</a>
<ul class=toc>
<li><a href=#column-combinator><span class=secno>14.1</span> Column combinator</a>
<li><a href=#the-nth-column-pseudo><span class=secno>14.2</span> <span class=css data-link-type=maybe title=:nth-column()>:nth-column()</span> pseudo-class</a>
<li><a href=#the-nth-last-column-pseudo><span class=secno>14.3</span> <span class=css data-link-type=maybe title=:nth-last-column()>:nth-last-column()</span> pseudo-class</a></ul>
<li><a href=#specificity><span class=secno>15</span> Calculating a selector’s specificity</a>
<li><a href=#grammar><span class=secno>16</span><span id=formal-syntax></span> Grammar</a>
<li><a href=#api-hooks><span class=secno>17</span> API Hooks</a>
<ul class=toc>
<li><a href=#parse-a-selector><span class=secno>17.1</span> Parse A Selector</a>
<li><a href=#parse-a-relative-selector><span class=secno>17.2</span> Parse A Relative Selector</a></ul>
<li><a href=#changes><span class=secno>18</span> Changes</a>
<li><a href=#acknowledgements><span class=secno>19</span> Acknowledgements</a>
<li><a href=#conformance><span class=secno></span> Conformance</a>
<ul class=toc>
<li><a href=#conventions><span class=secno></span> Document conventions</a>
<li><a href=#conformance-classes><span class=secno></span> Conformance classes</a>
<li><a href=#partial><span class=secno></span> Partial implementations</a>
<li><a href=#experimental><span class=secno></span> Experimental implementations</a>
<li><a href=#testing><span class=secno></span> Non-experimental implementations</a></ul>
<li><a href=#references><span class=secno></span> References</a>
<ul class=toc>
<li><a href=#normative><span class=secno></span> Normative References</a>
<li><a href=#informative><span class=secno></span> Informative References</a></ul>
<li><a href=#index><span class=secno></span> Index</a>
<li><a href=#property-index><span class=secno></span> Property index</a>
<li><a href=#issues-index><span class=secno></span>Issues Index</a></ul></div>
<h2 class="heading settled heading" data-level=1 id=context><span class=secno>1 </span><span class=content>
Introduction</span><a class=self-link href=#context></a></h2>
<p> <em>This section is not normative.</em>
<p> A selector is a boolean predicate
that takes an element in a tree structure
and tests whether the element matches the selector or not.
<p> These expressions may be used for many things:
<p> <ul>
<li>
directly on an element to test whether it matches some criteria,
such as in the <code>element.matches()</code> function defined in <a data-biblio-type=informative data-link-type=biblio href=#dom title=dom>[DOM]</a>
<li>
applied to an entire tree of elements
to filter it into a set of elements that match the criteria,
such as in the <code>document.queryAll()</code> function defined in <a data-biblio-type=informative data-link-type=biblio href=#dom title=dom>[DOM]</a>
or the selector of a CSS style rule.
<li>
used "in reverse" to generate markup that would match a given selector,
such as in <a href=http://haml.info/>HAML</a> or <a href=http://en.wikipedia.org/wiki/Zen_Coding>Zen Coding</a>
</ul>
<p> Selectors Levels 1, 2, and 3 are defined as the subsets of selector
functionality defined in the <a href=http://www.w3.org/TR/REC-CSS1>CSS1</a>,
<a href=http://www.w3.org/TR/CSS21/>CSS2.1</a>, and
<a href=http://www.w3.org/TR/css3-selectors/>Selectors Level 3</a>
specifications, respectively. This module defines Selectors Level 4.
<h3 class="heading settled heading" data-level=1.1 id=placement><span class=secno>1.1 </span><span class=content>Module Interactions</span><a class=self-link href=#placement></a></h3>
<p> This module replaces the definitions of
and extends the set of selectors defined for CSS in <a data-biblio-type=informative data-link-type=biblio href=#select title=select>[SELECT]</a> and <a data-biblio-type=informative data-link-type=biblio href=#css21 title=css21>[CSS21]</a>.
<p> Pseudo-element selectors,
which define abstract elements in a rendering tree,
are not part of this specification:
their generic syntax is described here,
but, due to their close integration with the rendering model and irrelevance to other uses such as DOM queries,
they will be defined in other modules.
<h2 class="heading settled heading" data-level=2 id=overview><span class=secno>2 </span><span class=content>
Selectors Overview</span><a class=self-link href=#overview></a></h2>
<p> <em>This section is non-normative, as it merely summarizes the
following sections.</em>
<p> A selector represents a structure. This structure can be used as a
condition (e.g. in a CSS rule) that determines which elements a
selector matches in the document tree, or as a flat description of the
HTML or XML fragment corresponding to that structure.
<p> Selectors may range from simple element names to rich contextual
representations.
<p> The following table summarizes the Selector syntax:
<table class=data>
<col class=pattern>
<col class=meaning>
<col class=section>
<col class=level>
<thead>
<tr>
<th>Pattern
<th>Represents
<th>Section
<th>Level
<tbody>
<tr>
<td><code>*</code>
<td>any element
<td><a href=#universal-selector>Universal selector</a>
<td>2
<tr>
<td><code>E</code>
<td>an element of type E
<td><a href=#type-selectors>Type (tag name) selector</a>
<td>1
<tbody>
<tr>
<td><code>E:not(<var>s1</var>, <var>s2</var>)</code>
<td>an E element that does not match either <a data-link-type=dfn href=#compound title="compound selector">compound selector</a> <var>s1</var>
or <a data-link-type=dfn href=#compound title="compound selector">compound selector</a> <var>s2</var>
<td><a href=#negation>Negation pseudo-class</a>
<td>3/4
<tr>
<td><code>E:matches(<var>s1</var>, <var>s2</var>)</code>
<td>an E element that matches <a data-link-type=dfn href=#compound title="compound selector">compound selector</a> <var>s1</var>
and/or <a data-link-type=dfn href=#compound title="compound selector">compound selector</a> <var>s2</var>
<td><a href=#matches>Matches-any pseudo-class</a>
<td>4
<tbody>
<tr>
<td><code>E.warning</code>
<td>an E element belonging to the class <code>warning</code>
(the document language specifies how class is determined).
<td><a href=#class-html>Class selectors</a>
<td>1
<tr>
<td><code>E#myid</code>
<td>an E element with ID equal to <code>myid</code>.
<td><a href=#id-selectors>ID selectors</a>
<td>1
<tr>
<td><code>E[foo]</code>
<td>an E element with a <code>foo</code> attribute
<td><a href=#attribute-selectors>Attribute selectors</a>
<td>2
<tr>
<td><code>E[foo="bar"]</code>
<td>an E element whose <code>foo</code> attribute value is
exactly equal to <code>bar</code>
<td><a href=#attribute-selectors>Attribute selectors</a>
<td>2
<tr>
<td><code>E[foo="bar" i]</code>
<td>an E element whose <code>foo</code> attribute value is
exactly equal to any (ASCII-range) case-permutation of <code>bar</code>
<td><a href=#attribute-case>Attribute selectors: Case-sensitivity</a>
<td>4
<tr>
<td><code>E[foo~="bar"]</code>
<td>an E element whose <code>foo</code> attribute value is
a list of whitespace-separated values, one of which is
exactly equal to <code>bar</code>
<td><a href=#attribute-selectors>Attribute selectors</a>
<td>2
<tr>
<td><code>E[foo^="bar"]</code>
<td>an E element whose <code>foo</code> attribute value
begins exactly with the string "bar"
<td><a href=#attribute-selectors>Attribute selectors</a>
<td>3
<tr>
<td><code>E[foo$="bar"]</code>
<td>an E element whose <code>foo</code> attribute value
ends exactly with the string <code>bar</code>
<td><a href=#attribute-selectors>Attribute selectors</a>
<td>3
<tr>
<td><code>E[foo*="bar"]</code>
<td>an E element whose <code>foo</code> attribute value
contains the substring <code>bar</code>
<td><a href=#attribute-selectors>Attribute selectors</a>
<td>3
<tr>
<td><code>E[foo|="en"]</code>
<td>an E element whose <code>foo</code> attribute value is
a hyphen-separated list of values beginning with <code>en</code>
<td><a href=#attribute-selectors>Attribute selectors</a>
<td>2
<tbody>
<tr>
<td><code>E:dir(ltr)</code>
<td>an element of type E in with left-to-right directionality
(the document language specifies how directionality is determined)
<td><a href=#dir-pseudo>The :dir() pseudo-class</a>
<td>4
<tr>
<td><code>E:lang(zh, *-hant)</code>
<td>an element of type E tagged as being either in Chinese
(any dialect or writing system)
or othewise written with traditional Chinese characters
<td><a href=#lang-pseudo>The :lang() pseudo-class</a>
<td>2/4
<tbody>
<tr>
<td><code>E:any-link</code>
<td>an E element being the source anchor of a hyperlink
<td><a href=#any-link-pseudo>The hyperlink pseudo-class</a>
<td>4
<tr>
<td><code>E:link</code>
<td>an E element being the source anchor of a hyperlink
of which the target is not yet visited
<td><a href=#link>The link history pseudo-classes</a>
<td>1
<tr>
<td><code>E:visited</code>
<td>an E element being the source anchor of a hyperlink
of which the target is already visited
<td><a href=#link>The link history pseudo-classes</a>
<td>1
<tr>
<td><code>E:local-link</code>
<td>an E element being the source anchor of a hyperlink
of which the target is the current document
<td><a href=#local-pseudo>The local link pseudo-class</a>
<td>4
<tr>
<td><code>E:local-link(0)</code>
<td>an E element being the source anchor of a hyperlink
of which the target is within the current domain
<td><a href=#local-pseudo>The local link pseudo-class</a>
<td>4
<tr>
<td><code>E:target</code>
<td>an E element being the target of the referring URL
<td><a href=#target-pseudo>The target pseudo-class</a>
<td>3
<tr>
<td><code>E:scope</code>
<td>an E element being a designated reference element
<td><a href=#scope-pseudo>The scope pseudo-class</a>
<td>4
<tbody>
<tr>
<td><code>E:current</code>
<td>an E element that is currently presented in a time-dimensional canvas
<td><a href=#time-pseudos>Time-dimensional Pseudo-classes</a>
<td>4
<tr>
<td><code>E:current(<var>s</var>)</code>
<td>an E element that is the deepest <a class=css data-link-type=maybe href=#current-pseudo title=:current>:current</a> element that
matches selector <var>s</var>
<td><a href=#time-pseudos>Time-dimensional Pseudo-classes</a>
<td>4
<tr>
<td><code>E:past</code>
<td>an E element that is in the past in a time-dimensional canvas
<td><a href=#time-pseudos>Time-dimensional Pseudo-classes</a>
<td>4
<tr>
<td><code>E:future</code>
<td>an E element that is in the future in a time-dimensional canvas
<td><a href=#time-pseudos>Time-dimensional Pseudo-classes</a>
<td>4
<tbody>
<tr>
<td><code>E:active</code>
<td>an E element that is in an activated state
<td><a href=#useraction-pseudos>The user action pseudo-classes</a>
<td>1
<tr>
<td><code>E:hover</code>
<td>an E element that is under the cursor,
or that has a descendant under the cursor
<td><a href=#useraction-pseudos>The user action pseudo-classes</a>
<td>2
<tr>
<td><code>E:focus</code>
<td>an E element that has user input focus
<td><a href=#useraction-pseudos>The user action pseudo-classes</a>
<td>2
<tr>
<td><code>E:active-drop</code>
<td>an E element that will receive the item currently being dragged
<td><a href=#drag-pseudos>The drag-and-drop pseudo-classes</a>
<td>4
<tr>
<td><code>E:valid-drop</code>
<td>an E element that could receive the item currently being dragged
<td><a href=#drag-pseudos>The drag-and-drop pseudo-classes</a>
<td>4
<tr>
<td><code>E:invalid-drop</code>
<td>an E element that cannot receive the item currently being dragged, but could receive some other item
<td><a href=#drag-pseudos>The drag-and-drop pseudo-classes</a>
<td>4
<tbody>
<tr>
<td><code>E:enabled<br>E:disabled</code>
<td>a user interface element E that is enabled or disabled, respectively
<td><a href=#enableddisabled>The :enabled and :disabled pseudo-classes</a>
<td>3
<tr>
<td><code>E:read-only</code><br><code>E:read-write</code>
<td>a user interface element E that
<td><a href=#rw-pseudos>The mutability pseudo-classes</a>
<td>3-UI/4
<tr>
<td><code>E:placeholder-shown</code>
<td>an input control currently showing placeholder text
<td><a href=#rw-pseudos>The placeholder-shown pseudo-class</a>
<td>3-UI/4
<tr>
<td><code>E:default</code>
<td>a user interface element E that
<td><a href=#default-pseudo>The default option pseudo-class :default</a>
<td>3-UI/4
<tr>
<td><code>E:checked</code>
<td>a user interface element E that is checked/selected
(for instance a radio-button or checkbox)
<td><a href=#checked>The selected-option pseudo-class</a>
<td>3
<tr>
<td><code>E:indeterminate</code>
<td>a user interface element E that is in an indeterminate state
(neither checked nor unchecked)
<td><a href=#indeterminate>The indeterminate-value pseudo-class</a>
<td>4
<tr>
<td><code>E:valid</code><br><code>E:invalid</code>
<td>a user-input element E that
<td><a href=#range-pseudos>The validity pseudo-classes</a>
<td>3-UI/4
<tr>
<td><code>E:in-range</code><br><code>E:out-of-range</code>
<td>a user-input element E whose value is in-range/out-of-range
<td><a href=#range-pseudos>The range pseudo-classes</a>
<td>3-UI/4
<tr>
<td><code>E:required</code><br><code>E:optional</code>
<td>a user-input element E that requires/does not require input
<td><a href=#opt-pseudos>The optionality pseudo-classes</a>
<td>3-UI/4
<tr>
<td><code>E:required</code><br><code>E:optional</code>
<td>a user-input element E with incorrect input
<td><a href=#opt-pseudos>The optionality pseudo-classes</a>
<td>4
<tbody>
<tr>
<td><code>E:root</code>
<td>an E element, root of the document
<td><a href=#structural-pseudos>Structural pseudo-classes</a>
<td>3
<tr>
<td><code>E:empty</code>
<td>an E element that has no children (not even text nodes)
<td><a href=#structural-pseudos>Structural pseudo-classes</a>
<td>3
<tr>
<td><code>E:blank</code>
<td>an E element that has no content except maybe white space
<td><a href=#structural-pseudos>Structural pseudo-classes</a>
<td>4
<tr>
<td><code>E:nth-child(<var>n</var>)</code>
<td>an E element, the <var>n</var>-th child of its parent
<td><a href=#structural-pseudos>Structural pseudo-classes</a>
<td>3
<tr>
<td><code>E:nth-last-child(<var>n</var>)</code>
<td>an E element, the <var>n</var>-th child of its parent,
counting from the last one
<td><a href=#structural-pseudos>Structural pseudo-classes</a>
<td>3
<tr>
<td><code>E:first-child</code>
<td>an E element, first child of its parent
<td><a href=#structural-pseudos>Structural pseudo-classes</a>
<td>2
<tr>
<td><code>E:last-child</code>
<td>an E element, last child of its parent
<td><a href=#structural-pseudos>Structural pseudo-classes</a>
<td>3
<tr>
<td><code>E:only-child</code>
<td>an E element, only child of its parent
<td><a href=#structural-pseudos>Structural pseudo-classes</a>
<td>3
<tr>
<td><code>E:nth-of-type(<var>n</var>)</code>
<td>an E element, the <var>n</var>-th sibling of its type
<td><a href=#structural-pseudos>Structural pseudo-classes</a>
<td>3
<tr>
<td><code>E:nth-last-of-type(<var>n</var>)</code>
<td>an E element, the <var>n</var>-th sibling of its type,
counting from the last one
<td><a href=#structural-pseudos>Structural pseudo-classes</a>
<td>3
<tr>
<td><code>E:first-of-type</code>
<td>an E element, first sibling of its type
<td><a href=#structural-pseudos>Structural pseudo-classes</a>
<td>3
<tr>
<td><code>E:last-of-type</code>
<td>an E element, last sibling of its type
<td><a href=#structural-pseudos>Structural pseudo-classes</a>
<td>3
<tr>
<td><code>E:only-of-type</code>
<td>an E element, only sibling of its type
<td><a href=#structural-pseudos>Structural pseudo-classes</a>
<td>3
<tr>
<td><code>E:nth-match(<var>n</var> of <var>selector</var>)</code>
<td>an E element, the <var>n</var>-th sibling matching <var>selector</var>
<td><a href=#structural-pseudos>Structural pseudo-classes</a>
<td>4
<tr>
<td><code>E:nth-last-match(<var>n</var> of <var>selector</var>)</code>
<td>an E element, the <var>n</var>-th sibling matching <var>selector</var>,
counting from the last one
<td><a href=#structural-pseudos>Structural pseudo-classes</a>
<td>4
<tbody>
<tr>
<td><code>E F</code>
<td>an F element descendant of an E element
<td><a href=#descendant-combinators>Descendant combinator</a>
<td>1
<tr>
<td><code>E > F</code>
<td>an F element child of an E element
<td><a href=#child-combinators>Child combinator</a>
<td>2
<tr>
<td><code>E + F</code>
<td>an F element immediately preceded by an E element
<td><a href=#adjacent-sibling-combinators>Next-sibling combinator</a>
<td>2
<tr>
<td><code>E ~ F</code>
<td>an F element preceded by an E element
<td><a href=#general-sibling-combinators>Following-sibling combinator</a>
<td>3
<tr>
<td><code>E /foo/ F</code>
<td>an F element ID-referenced by an E element’s <code>foo</code> attribute
<td><a href=#idref-combinators>Reference combinator</a>
<td>4
<tr>
<td><code>!E > F</code>
<td>an E element parent of an F element
<td><a href=#subject>Determining the subject of a selector</a> +
<a href=#child-combinators>Child combinator</a>
<td>4
<tbody>
<tr>
<td><code>F || E</code>
<td>an E element that represents a cell in a grid/table
belonging to a column represented by an element F
<td><a href=#table-pseudos>Grid-Structural pseudo-classes</a>
<td>4
<tr>
<td><code>E:nth-column(<var>n</var>)</code>
<td>an E element that represents a cell belonging to the
<var>n</var>th column in a grid/table
<td><a href=#table-pseudos>Grid-Structural pseudo-classes</a>
<td>4
<tr>
<td><code>E:nth-last-column(<var>n</var>)</code>
<td>an E element that represents a cell belonging to the
<var>n</var>th column in a grid/table, counting from the last one
<td><a href=#table-pseudos>Grid-Structural pseudo-classes</a>
<td>4
</table>
<p class=note> Note: Some Level 4 selectors (noted above as "3-UI") were introduced in <a data-biblio-type=informative data-link-type=biblio href=#css3ui title=css3ui>[CSS3UI]</a>.
<h3 class="heading settled heading" data-level=2.1 id=profiles><span class=secno>2.1 </span><span class=content>
<a data-link-type=dfn href=#fast-profile title=fast>Fast</a> vs <a data-link-type=dfn href=#complete-profile title=complete>Complete</a> Selector Profiles</span><a class=self-link href=#profiles></a></h3>
<p> Selectors are used in many different contexts,
with wildly varying performance characteristics.
Some powerful selectors are unfortunately too slow
to realistically include in the more performance-sensitive contexts.
To accommodate this, two profiles of the Selectors spec are defined:
<dl>
<dt><dfn data-dfn-type=dfn data-noexport="" id=fast-profile>fast<a class=self-link href=#fast-profile></a></dfn>
<dd>
The <a data-link-type=dfn href=#fast-profile title=fast>fast</a> profile is appropriate for use in any context,
including dynamic browser CSS selector matching.
It includes every selector defined in this document,
except for:
<p> <ul>
<li><a data-link-type=dfn href=#combinator title=combinators>Combinators</a> within <a class=css data-link-type=maybe href=#matches-pseudo title=:matches()>:matches()</a>, <a class=css data-link-type=maybe href=#negation-pseudo title=:not()>:not()</a>, <a class=css data-link-type=maybe href=#nth-match-pseudo title=:nth-match()>:nth-match()</a>, and <a class=css data-link-type=maybe href=#nth-last-match-pseudo title=:nth-last-match()>:nth-last-match()</a>.
<p class=issue id=issue-d60bc5a1><a class=self-link href=#issue-d60bc5a1></a>We are considering whether this restriction should be lifted.
<li>The <a href=#idref-combinators>reference combinator</a>
<li>The <a href=#subject>subject indicator</a>
</ul>
<dt><dfn data-dfn-type=dfn data-noexport="" id=complete-profile>complete<a class=self-link href=#complete-profile></a></dfn>
<dd>
The <a data-link-type=dfn href=#complete-profile title=complete>complete</a> profile is appropriate for contexts which aren’t extremely performance sensitive.
For example, the <a class=idl-code data-link-for=Element data-link-type=method title=query()>query()</a> method defined in <a data-biblio-type=informative data-link-type=biblio href=#dom title=dom>[DOM]</a> should use the <a class=css data-link-type=maybe href=#complete-profile title=complete>complete</a> profile.
It includes all of the selectors defined in this document.
</dl>
<p> CSS implementations conformant to Selectors Level 4 must use the <a class=css data-link-type=maybe href=#fast-profile title=fast>fast</a> profile for CSS selection.
<p class=issue id=issue-cbdc0c66><a class=self-link href=#issue-cbdc0c66></a>
The categorization of things into the "fast" or "complete" profiles needs implementor review.
If some things currently not in the fast profile can reasonably be done in CSS Selectors,
we should move them.
<h2 class="heading settled heading" data-level=3 id=syntax><span class=secno>3 </span><span class=content>
Selector Syntax and Structure</span><a class=self-link href=#syntax></a></h2>
<h3 class="heading settled heading" data-level=3.1 id=structure><span class=secno>3.1 </span><span class=content>
Structure and Terminology</span><a class=self-link href=#structure></a></h3>
<p> The term <dfn data-dfn-type=dfn data-export="" id=selector>selector<a class=self-link href=#selector></a></dfn> can refer to a <a data-link-type=dfn href=#simple title="simple selector">simple selector</a>,
<a data-link-type=dfn href=#compound title="compound selector">compound selector</a>, <a data-link-type=dfn href=#complex title="complex selector">complex selector</a>, or <a data-link-type=dfn href=#selector-list title="selector list">selector list</a>.
<p> A <a data-link-type=dfn href=#selector-list title="selector list">selector list</a> is a comma-separated list of <a data-link-type=dfn href=#selector title=selectors>selectors</a>;
see <a href=#grouping>Selector Lists</a>.
<p> A <dfn data-dfn-type=dfn data-export="" id=complex>complex selector<a class=self-link href=#complex></a></dfn> is a sequence of one or more <a data-link-type=dfn href=#compound title="compound selectors">compound selectors</a>
separated by <a data-link-type=dfn href=#combinator title=combinators>combinators</a>.
<p> A <dfn data-dfn-type=dfn data-export="" id=compound>compound selector<a class=self-link href=#compound></a></dfn>
is a sequence of <a data-link-type=dfn href=#simple title="simple selectors">simple selectors</a>
that are not separated by a <a data-link-type=dfn href=#combinator title=combinator>combinator</a>.
If it contains a <a data-link-type=dfn href=#type-selector title="type selector">type selector</a> or <a data-link-type=dfn href=#universal-selector0 title="universal selector">universal selector</a>,
that selector comes first in the sequence.
Only one type selector or universal selector is allowed in the sequence.
<p> A <dfn data-dfn-type=dfn data-export="" id=simple>simple selector<a class=self-link href=#simple></a></dfn> represents an aspect of an element to be matched against.
A simple selector is either a
<a data-link-type=dfn href=#type-selector title="type selector">type selector</a>,
<a data-link-type=dfn href=#universal-selector0 title="universal selector">universal selector</a>,
<a data-link-type=dfn href=#attribute-selector title="attribute selector">attribute selector</a>,
<a data-link-type=dfn href=#class-selector title="class selector">class selector</a>,
<a data-link-type=dfn href=#id-selector title="id selector">ID selector</a>,
or <a data-link-type=dfn href=#pseudo-class title=pseudo-class>pseudo-class</a>.
<p> A <dfn data-dfn-type=dfn data-export="" id=combinator>combinator<a class=self-link href=#combinator></a></dfn> represents a particular kind of relationship
between the elements matched by the <a data-link-type=dfn href=#compound title="compound selectors">compound selectors</a> on either side.
Combinators in Selectors level 4 include:
whitespace,
“greater-than sign” (U+003E, <code>></code>),
“plus sign” (U+002B, <code>+</code>),
and “tilde” (U+007E, <code>~</code>).
<p class=issue id=issue-2c7c31ce><a class=self-link href=#issue-2c7c31ce></a> Fill in more combinators.
<p> An empty selector,
containing no <a data-link-type=dfn href=#compound title="compound selector">compound selector</a>,
is an <a href=#invalid>invalid selector</a>.
<p class=note> Note: As whitespace is a valid <a data-link-type=dfn href=#combinator title=combinator>combinator</a>,
no whitespace is allowed between the <a data-link-type=dfn href=#simple title="simple selectors">simple selectors</a>
in a <a data-link-type=dfn href=#compound title="compound selector">compound selector</a>.
<h3 class="heading settled heading" data-level=3.2 id=evaluating-selectors><span class=secno>3.2 </span><span class=content>
Evaluating a Selector</span><a class=self-link href=#evaluating-selectors></a></h3>
<p> This section describes how to <dfn data-dfn-type=dfn data-export="" id=evaluate-a-selector>evaluate a selector<a class=self-link href=#evaluate-a-selector></a></dfn> against a set of elements.
<p> APIs using this algorithm must provide a selector,
and one or more <a data-link-type=dfn href=#element-tree title="element tree">element tree</a> root elements
indicating the trees that will be searched by the selector.
They may optionally provide:
<p> <ul>
<li>
a <a data-link-type=dfn href=#scoping-method- title="scoping method">scoping method</a> and <a data-link-type=dfn href=#scoping-root title="scoping root">scoping root</a>.
If not specified, the selector defaults to being unscoped.
<li>
a set of <a data-link-type=dfn href=#scope-element title=":scope elements">:scope elements</a>,
for resolving the <a class=css data-link-type=maybe href=#scope-pseudo title=:scope>:scope</a> pseudo-class against.
If not specified,
the set defaults to being empty.
<p> If the selector is a <a data-link-type=dfn href=#relative-selector- title="relative selector">relative selector</a>,
the set of <a data-link-type=dfn href=#scope-element title=":scope elements">:scope elements</a> must not be empty.
<p class=note> Note: Note that if the selector is scoped,
the scoping root is automatically taken as the <a data-link-type=dfn href=#scope-element title=":scope element">:scope element</a>,
so it doesn’t have to be provided explicitly
unless a different result is desired.
<li>
which <a data-link-type=dfn href=#pseudo-element title=pseudo-elements>pseudo-elements</a> are allowed to show up in the match list, if any.
If not specified, this defaults to allowing all pseudo-elements.
</ul>
<p> A <a data-link-type=dfn href=#selector title=selector>selector</a> is evaluated against some initial list of elements:
the <dfn data-dfn-type=dfn data-export="" id=selector-match-list>selector match list<a class=self-link href=#selector-match-list></a></dfn>.
The <a data-link-type=dfn href=#selector-match-list title="selector match list">selector match list</a> is initially populated with the <a data-link-type=dfn href=#element-tree title="element tree">element tree</a> roots
provided to the algorithm,
and all elements reachable from them by traversing any number of child lists.
<p> If the selector is <a data-link-type=dfn href=#scope-contained- title=scope-contained>scope-contained</a>,
the <a data-link-type=dfn href=#selector-match-list title="selector match list">selector match list</a> is immediately filtered
to contain only elements that are either the <a data-link-type=dfn href=#scoping-root title="scoping root">scoping root</a>
or descendants of the <a data-link-type=dfn href=#scoping-root title="scoping root">scoping root</a>.
<p> The selector is processed from left to right in order,
with <a data-link-type=dfn href=#simple title="simple selectors">simple selectors</a> filtering the <a data-link-type=dfn href=#selector-match-list title="selector match list">selector match list</a>,
and <a data-link-type=dfn href=#combinator title=combinators>combinators</a> and <a data-link-type=dfn href=#pseudo-element title=pseudo-elements>pseudo-elements</a> changing the <a data-link-type=dfn href=#selector-match-list title="selector match list">selector match list</a> into something new.
If the selector is <a data-link-type=dfn href=#scope-contained- title=scope-contained>scope-contained</a>
then after each <a data-link-type=dfn href=#combinator title=combinator>combinator</a>
the <a data-link-type=dfn href=#selector-match-list title="selector match list">selector match list</a> must be filtered
to contain only elements that are either the <a data-link-type=dfn href=#scoping-root title="scoping root">scoping root</a>
or descendants of the <a data-link-type=dfn href=#scoping-root title="scoping root">scoping root</a>.
<p> If the selector is <a data-link-type=dfn href=#scope-filtered- title=scope-filtered>scope-filtered</a>,
then after the selector is finished processing,
the <a data-link-type=dfn href=#selector-match-list title="selector match list">selector match list</a> must be filtered
to contain only elements that are either the <a data-link-type=dfn href=#scoping-root title="scoping root">scoping root</a>
or descendants of the <a data-link-type=dfn href=#scoping-root title="scoping root">scoping root</a>.
<p> After the selector is finished matching,
the <a data-link-type=dfn href=#selector-match-list title="selector match list">selector match list</a> must be filtered
to only contain elements and <a data-link-type=dfn href=#pseudo-element title=pseudo-elements>pseudo-elements</a>
allowed by the invoker of this algorithm.
<p> When this process is done, the elements in the <a data-link-type=dfn href=#selector-match-list title="selector match list">selector match list</a>
are the elements said to match the selector.
If the order of elements matter,
they must be sorted in document order,
unless otherwise specified.
<div class=example>
For example, to evaluate the selector "div > i.name" against a document,
the <a data-link-type=dfn href=#selector-match-list title="selector match list">selector match list</a> is first set to all the elements in the entire document.
Then, the "div" type selector is evaluated, filtering the <a data-link-type=dfn href=#selector-match-list title="selector match list">selector match list</a>
to only contain elements with a tagname of "div".
Then, the ">" child combinator is evaluated, transforming the <a data-link-type=dfn href=#selector-match-list title="selector match list">selector match list</a>
by replacing each element currently in it with the element’s children.
Then, the "i" type selector is evaluated, filtering the <a data-link-type=dfn href=#selector-match-list title="selector match list">selector match list</a>
to only contain elements with a tagname of "i".
Finally, the ".name" class selector is evaluated, filter the <a data-link-type=dfn href=#selector-match-list title="selector match list">selector match list</a>
to only contain elements with a class of "name".
</div>
<p class=note> Note: Many implementations of selectors instead evaluate them right to left,
as it’s more efficient to do so in many cases.
This, as usual, is completely valid,
as long as it results in the same elements being returned
as the spec’s algorithm would.
<p class=issue id=issue-1bcc9de6><a class=self-link href=#issue-1bcc9de6></a> The relative position of pseudo-elements in the <a data-link-type=dfn href=#selector-match-list title="selector match list">selector match list</a> is undefined.
There’s not yet a context that exposes this information,
but we need to decide on something eventually,
before something <em>is</em> exposed.
<h3 class="heading settled heading" data-level=3.3 id=data-model><span class=secno>3.3 </span><span class=content>
Data Model</span><a class=self-link href=#data-model></a></h3>
<p> Selectors are matched against an <dfn data-dfn-type=dfn data-export="" id=element-tree>element tree<a class=self-link href=#element-tree></a></dfn>,
which is an abstract tree structure containing elements
having the structure defined in the <a href=http://dom.spec.whatwg.org/#trees>DOM Standard</a> <a data-biblio-type=normative data-link-type=biblio href=#dom title=dom>[DOM]</a>.
<p> Each element may have any of:
<p> <ul>
<li>A type, which is a pair of strings: a namespace and a local name.
<li>An ID, which is a string.
<li>Classes, which are strings.
<li>Attributes, which are pairs of strings consisting of an attribute name and an attribute value.
<li>A list of child elements.
<li>Arbitrary additional information,
which isn’t directly accessible,
but can be used in the matching of pseudo-classes and pseudo-elements.
</ul>
<p> The first four bullet points in the list above are referred to as <dfn data-dfn-type=dfn data-export="" id=feature title=feature>features<a class=self-link href=#feature></a></dfn>.
The <a data-link-type=dfn href=#simple title="simple selectors">simple selectors</a> which are keyed off of them
(<a data-link-type=dfn href=#universal-selector0 title="universal selector">universal selector</a>, <a data-link-type=dfn href=#type-selector title="type selectors">type selectors</a>, <a data-link-type=dfn href=#id-selector title="id selectors">ID selectors</a>, <a data-link-type=dfn href=#class-selector title="class selectors">class selectors</a>, and <a data-link-type=dfn href=#attribute-selector title="attribute selectors">attribute selectors</a>)
are called <dfn data-dfn-type=dfn data-export="" id=feature-selector title="feature selector">feature selectors<a class=self-link href=#feature-selector></a></dfn>.
<p> While elements may lack any of the individual <a data-link-type=dfn href=#feature title=features>features</a>,
some elements are <dfn data-dfn-type=dfn data-export="" id=featureless>featureless<a class=self-link href=#featureless></a></dfn>,
which means that not only do they lack any <a data-link-type=dfn href=#feature title=features>features</a>
(and thus will never match a <a data-link-type=dfn href=#feature-selector title="feature selector">feature selector</a>),
but any selectors that reference <a data-link-type=dfn href=#feature title=features>features</a>,
such as <span class=css data-link-type=maybe title=:not(div)>:not(div)</span>,
also never match them.
Thus, only <a data-link-type=dfn href=#pseudo-class title=pseudo-classes>pseudo-classes</a> or <a data-link-type=dfn href=#pseudo-element title=pseudo-elements>pseudo-elements</a> can be used to select them.
Individual <a data-link-type=dfn href=#featureless title=featureless>featureless</a> elements may define additional restrictions on what kinds of selectors can match them.
(For example, the <a data-link-type=dfn href=http://dev.w3.org/csswg/css-scoping-1/#host-element0 title="host element">host element</a> in a <a data-link-type=dfn href=http://dev.w3.org/csswg/css-scoping-1/#shadow-tree title="shadow tree">shadow tree</a> is <a data-link-type=dfn href=#featureless title=featureless>featureless</a>,
and can’t be matched by <em>any</em> <a data-link-type=dfn href=#pseudo-class title=pseudo-class>pseudo-class</a> except for <a class=css data-link-type=maybe href=http://dev.w3.org/csswg/css-scoping-1/#selectordef-host0 title=:host>:host</a> and <a class=css data-link-type=maybe href=http://dev.w3.org/csswg/css-scoping-1/#selectordef-host-context title=:host-context()>:host-context()</a>.)
<p> In a DOM document,
the DOM is used as the <a data-link-type=dfn href=#element-tree title="element tree">element tree</a>.
Each DOM element is an element in the <a data-link-type=dfn href=#element-tree title="element tree">element tree</a>,
with the DOM element’s namespace and local name as the type,
and its ID, class list, attributes, and child elements
as the ID, classes, attributes, and child elements in the <a data-link-type=dfn href=#element-tree title="element tree">element tree</a>.
The rest of the information in the DOM is also accessible
as the arbitrary additional information in the <a data-link-type=dfn href=#element-tree title="element tree">element tree</a>.
<h3 class="heading settled heading" data-level=3.4 id=scoping><span class=secno>3.4 </span><span class=content>
Scoped Selectors</span><a class=self-link href=#scoping></a></h3>
<p> Some host applications may choose to <dfn data-dfn-type=dfn data-export="" id=scope- title="scope | scoped selector">scope<a class=self-link href=#scope-></a></dfn> selectors
to a particular subtree or fragment of the document.
The root of the scoping subtree is called the <dfn data-dfn-type=dfn data-export="" id=scoping-root>scoping root<a class=self-link href=#scoping-root></a></dfn>,
and may be either a true element (the <dfn data-dfn-type=dfn data-export="" id=scoping-element>scoping element<a class=self-link href=#scoping-element></a></dfn>)
or a <dfn data-dfn-type=dfn data-export="" id=virtual-scoping-root title="virtual scoping root">virtual<a class=self-link href=#virtual-scoping-root></a></dfn> one (such as a <a class=idl-code data-link-type=interface href=http://dom.spec.whatwg.org/#documentfragment title=documentfragment>DocumentFragment</a>).
<p> There are two <dfn data-dfn-type=dfn data-export="" id=scoping-method- title="scoping method | selector scoping method">scoping methods<a class=self-link href=#scoping-method-></a></dfn> for selectors:
<dl>
<dt><dfn data-dfn-type=dfn data-export="" id=scope-contained- title="scope-contained | scope-contained selector">scope-contained<a class=self-link href=#scope-contained-></a></dfn>
<dd>
With this method of scoping, selectors match as if
the <a data-link-type=dfn href=#scoping-root title="scoping root">scoping root</a> were the root of the document:
all <a data-link-type=dfn href=#compound title="compound selectors">compound selectors</a> must be represented within the scope.
(The <a class=css data-link-type=maybe href=#root-pseudo title=:root>:root</a> pseudo-class, however,
still only matches the actual root of the document.)
<dt><dfn data-dfn-type=dfn data-export="" id=scope-filtered- title="scope-filtered | scope-filtered selector">scope-filtered<a class=self-link href=#scope-filtered-></a></dfn>
<dd>
With this method of scoping, a selector matches an element only if the element is within the scope,
even if other components of the selector are outside the scope.
(A <a data-link-type=dfn href=#scoping-element title="scoping element">scoping element</a> is considered to be in scope.)
</dl>
<div class=example>
For example,
the <code>element.querySelector()</code> function defined in <a data-biblio-type=informative data-link-type=biblio href=#dom title=dom>[DOM]</a>
allows the author to define a <a data-link-type=dfn href=#scope-filtered- title=scope-filtered>scope-filtered</a> selector.
<p> On the other hand, the selectors within an <a data-biblio-type=informative data-link-type=biblio href=#html5 title=html5>[HTML5]</a> scoped stylesheet
define <a data-link-type=dfn href=#scope-contained- title=scope-contained>scope-contained</a> selectors.
</div>
<p class=note> Note: If there are no <a data-link-type=dfn href=#scope-element title=":scope elements">:scope elements</a> when a selector is evaluated,
the <a data-link-type=dfn href=#scoping-root title="scoping root">scoping root</a> acts like a <a data-link-type=dfn href=#scope-element title=":scope element">:scope element</a>.
<h3 class="heading settled heading" data-level=3.5 id=relative><span class=secno>3.5 </span><span class=content>
Relative Selectors</span><a class=self-link href=#relative></a></h3>
<p> Certain contexts may accept <dfn data-dfn-type=dfn data-export="" id=relative-selector- title="relative selector | relative | scope-relative">relative selectors<a class=self-link href=#relative-selector-></a></dfn>,
which are a shorthand for selectors that represent elements relative to a <a data-link-type=dfn href=#scope-element title=":scope element">:scope element</a>
(i.e. an element that matches <a class=css data-link-type=maybe href=#scope-pseudo title=:scope>:scope</a>).
In a <a data-link-type=dfn href=#relative-selector- title="relative selector">relative selector</a>,
“:scope ” (the <a class=css data-link-type=maybe href=#scope-pseudo title=:scope>:scope</a> pseudo-class followed by a space)
is implied at the beginning of each <a data-link-type=dfn href=#complex title="complex selector">complex selector</a>
that does not already contain the <a class=css data-link-type=maybe href=#scope-pseudo title=:scope>:scope</a> pseudo-class.
This allows the selector to begin syntactically with a <a data-link-type=dfn href=#combinator title=combinator>combinator</a>.
However, it must be <a href=#absolutize>absolutized</a> before matching.
<p> Relative selectors, once absolutized,
can additionally be <a data-link-type=dfn href=#scope-contained- title=scope-contained>scope-contained</a> or <a data-link-type=dfn href=#scope-filtered- title=scope-filtered>scope-filtered</a>.
<h4 class="heading settled heading" data-level=3.5.1 id=absolutizing><span class=secno>3.5.1 </span><span class=content>
Absolutizing a Relative Selector</span><a class=self-link href=#absolutizing></a></h4>
<p> To <dfn data-dfn-type=dfn data-export="" id=absolutize>absolutize a relative selector<a class=self-link href=#absolutize></a></dfn>: