-
Notifications
You must be signed in to change notification settings - Fork 0
/
prototype.html
1859 lines (1261 loc) · 85.4 KB
/
prototype.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>
<!--
_ooOoo_
o8888888o
88" . "88
(| -_- |)
O\ = /O
____/`---'\____
.' \\| |// `.
/ \\||| : |||// \
/ _||||| -:- |||||- \
| | \\\ - /// | |
| \_| ''\---/'' | |
\ .-\__ `-` ___/-. /
___`. .' /--.--\ `. . __
."" '< `.___\_<|>_/___.' >'"".
| | : `- \`.;`\ _ /`;.`/ - ` : | |
\ \ `-. \_ __\ /__ _/ .-` / /
======`-.____`-.___\_____/___.-`____.-'======
`=---='
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
佛祖保佑 永无BUG
-->
<html class="theme-next mist use-motion" lang="zh-Hans">
<head>
<meta charset="UTF-8"/>
<link href="//mydearest.cn" rel="dns-prefetch">
<link href="//www.mydearest.cn" rel="dns-prefetch">
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1"/>
<meta name="theme-color" content="#222">
<meta name="description" content="陈宇的博客" />
<meta http-equiv="Cache-Control" content="no-transform" />
<meta http-equiv="Cache-Control" content="no-siteapp" />
<link href="//fonts.googleapis.com/css?family=Lato:300,300italic,400,400italic,700,700italic|Roboto Slab:300,300italic,400,400italic,700,700italic|Lobster Two:300,300italic,400,400italic,700,700italic|PT Mono:300,300italic,400,400italic,700,700italic&subset=latin,latin-ext" rel="stylesheet" type="text/css">
<meta name="keywords" content="原型链," />
<link rel="alternate" href="/rss2.xml" title="cosyer's Blog" type="application/atom+xml" />
<link rel="shortcut icon" type="image/x-icon" href="/images/favicon.ico" />
<meta name="description" content="原型对象的用途是为每个实例对象存储共享的方法和属性，它仅仅是一个普通对象而已，仅有一份。 每个对象都会在其内部初始化一个属性，就是prototype(原型)，当我们访问一个对象的属性时， 如果这个对象内部不存在这个属性，那么它就会去prototype里找这个属性，这个prototype又会有自己的prototype，于是就这样一直找下去，也就是我们平时所说的原型链的概念 “prototype”">
<meta property="og:type" content="article">
<meta property="og:title" content="JavaScript深入之从原型到原型链">
<meta property="og:url" content="http://mydearest.cn/prototype.html">
<meta property="og:site_name" content="cosyer's Blog">
<meta property="og:description" content="原型对象的用途是为每个实例对象存储共享的方法和属性，它仅仅是一个普通对象而已，仅有一份。 每个对象都会在其内部初始化一个属性，就是prototype(原型)，当我们访问一个对象的属性时， 如果这个对象内部不存在这个属性，那么它就会去prototype里找这个属性，这个prototype又会有自己的prototype，于是就这样一直找下去，也就是我们平时所说的原型链的概念 “prototype”">
<meta property="og:image" content="http://cdn.mydearest.cn/blog/images/prototype1.png">
<meta property="og:image" content="http://cdn.mydearest.cn/blog/images/prototype2.png">
<meta property="og:image" content="http://cdn.mydearest.cn/blog/images/prototype3.png">
<meta property="og:image" content="http://cdn.mydearest.cn/blog/images/prototype4.png">
<meta property="og:image" content="http://cdn.mydearest.cn/blog/images/prototype5.png">
<meta property="article:published_time" content="2018-06-12T11:47:24.000Z">
<meta property="article:modified_time" content="2020-08-27T15:26:50.983Z">
<meta property="article:author" content="陈宇（cosyer）">
<meta property="article:tag" content="原型链">
<meta name="twitter:card" content="summary">
<meta name="twitter:image" content="http://cdn.mydearest.cn/blog/images/prototype1.png">
<script type="text/javascript" id="hexo.configurations">
var NexT = window.NexT || {};
var CONFIG = {
root: '/',
scheme: 'Mist',
sidebar: {"position":"left","display":"always","offset":12,"offset_float":12,"b2t":false,"scrollpercent":false,"onmobile":false},
fancybox: true,
tabs: true,
motion: true,
duoshuo: {
userId: '0',
author: '博主'
},
algolia: {
applicationID: '',
apiKey: '',
indexName: '',
hits: {"per_page":10},
labels: {"input_placeholder":"Search for Posts","hits_empty":"We didn't find any results for the search: ${query}","hits_stats":"${hits} results found in ${time} ms"}
}
};
</script>
<link rel="canonical" href="http://mydearest.cn/prototype.html"/>
<title>JavaScript深入之从原型到原型链 | cosyer's Blog</title>
<script type="text/javascript">
var _hmt = _hmt || [];
(function() {
var hm = document.createElement("script");
hm.src = "https://hm.baidu.com/hm.js?653a4be35cb6c7b26817038a17c3f0d6";
var s = document.getElementsByTagName("script")[0];
s.parentNode.insertBefore(hm, s);
})();
</script>
<link href="https://mydearest.cn/css/all-9097fb9016.css" rel="stylesheet" type="text/css">
<style>
// scrollbar滚动条样式优化
::-webkit-scrollbar-corner {
background-color: transparent;
}
::-webkit-scrollbar-button {
width: 0;
height: 0;
display: none;
}
::-webkit-scrollbar-thumb {
width: 7px;
background-color: #b4babf;
border-radius: 7px;
}
::-webkit-scrollbar {
width: 7px;
height: 7px;
}
::-webkit-scrollbar-track {
width: 15px;
}
::-webkit-scrollbar:hover {
background-color: transparent;
}
* {
cursor: url("http://cdn.mydearest.cn/blog/images/miku1.png"),auto!important
}
:active {
cursor: url("http://cdn.mydearest.cn/blog/images/miku2.png"),auto!important
}
a:hover {
cursor: url("http://cdn.mydearest.cn/blog/images/miku2.png"),auto!important
}
</style>
<meta name="generator" content="Hexo 4.2.1"></head>
<body itemscope itemtype="http://schema.org/WebPage" lang="zh-Hans">
<div id="loader">
<div></div>
</div>
<div class="container sidebar-position-left page-post-detail ">
<div class="headband"></div>
<a href="https://github.com/cosyer" target="_blank" rel="noopener" class="github-corner" aria-label="View source on Github"><svg width="80" height="80" viewBox="0 0 250 250" style="fill:#151513; color:#fff; position: absolute; top: 0; border: 0; left: 0; transform: scale(-1, 1);" aria-hidden="true"><path d="M0,0 L115,115 L130,115 L142,142 L250,250 L250,0 Z"></path><path d="M128.3,109.0 C113.8,99.7 119.0,89.6 119.0,89.6 C122.0,82.7 120.5,78.6 120.5,78.6 C119.2,72.0 123.4,76.3 123.4,76.3 C127.3,80.9 125.5,87.3 125.5,87.3 C122.9,97.6 130.6,101.9 134.4,103.2" fill="currentColor" style="transform-origin: 130px 106px;" class="octo-arm"></path><path d="M115.0,115.0 C114.9,115.1 118.7,116.5 119.8,115.4 L133.7,101.6 C136.9,99.2 139.9,98.4 142.2,98.6 C133.8,88.0 127.5,74.4 143.8,58.0 C148.5,53.4 154.0,51.2 159.7,51.0 C160.3,49.4 163.2,43.6 171.4,40.1 C171.4,40.1 176.1,42.5 178.8,56.2 C183.1,58.6 187.2,61.8 190.9,65.4 C194.5,69.0 197.7,73.2 200.1,77.6 C213.8,80.2 216.3,84.9 216.3,84.9 C212.7,93.1 206.9,96.0 205.4,96.6 C205.1,102.4 203.0,107.8 198.3,112.5 C181.9,128.9 168.3,122.5 157.7,114.1 C157.9,116.9 156.7,120.9 152.7,124.9 L141.0,136.5 C139.8,137.7 141.6,141.9 141.8,141.8 Z" fill="currentColor" class="octo-body"></path></svg><style>.github-corner:hover .octo-arm{animation:octocat-wave 560ms ease-in-out}@keyframes octocat-wave{0%,100%{transform:rotate(0)}20%,60%{transform:rotate(-25deg)}40%,80%{transform:rotate(10deg)}}@media (max-width:500px){.github-corner:hover .octo-arm{animation:none}.github-corner .octo-arm{animation:octocat-wave 560ms ease-in-out}}</style></a>
<header id="header" class="header" itemscope itemtype="http://schema.org/WPHeader">
<div class="header-inner"><div class="site-brand-wrapper">
<div class="site-meta ">
<div class="custom-logo-site-title">
<a href="/" class="brand" rel="start">
<span class="logo-line-before"><i></i></span>
<span class="site-title">cosyer's Blog</span>
<span class="logo-line-after"><i></i></span>
</a>
</div>
<h1 class="site-subtitle" itemprop="description">Blog</h1>
</div>
<div class="site-nav-toggle">
<button>
<span class="btn-bar"></span>
<span class="btn-bar"></span>
<span class="btn-bar"></span>
</button>
</div>
</div>
<nav class="site-nav">
<ul id="menu" class="menu">
<li class="menu-item menu-item-home">
<a href="/" class="faa-parent animated-hover" rel="section">
<i class="menu-item-icon fa fa-fw fa-home faa-wrench"></i> <br />
首页
</a>
</li>
<li class="menu-item menu-item-links">
<a href="/links/" class="faa-parent animated-hover" rel="section">
<i class="menu-item-icon fa fa-fw fa-link faa-shake"></i> <br />
友链
</a>
</li>
<li class="menu-item menu-item-guestbook">
<a href="/guestbook/" class="faa-parent animated-hover" rel="section">
<i class="menu-item-icon fa fa-fw fa-comment-o faa-tada"></i> <br />
留言板
</a>
</li>
<li class="menu-item menu-item-archives">
<a href="/archives/" class="faa-parent animated-hover" rel="section">
<i class="menu-item-icon fa fa-fw fa-archive faa-float"></i> <br />
归档
</a>
</li>
<li class="menu-item menu-item-about">
<a href="/about/" class="faa-parent animated-hover" rel="section">
<i class="menu-item-icon fa fa-fw fa-user faa-horizontal"></i> <br />
关于
</a>
</li>
<li class="menu-item menu-item-search">
<a href="javascript:;" class="popup-trigger faa-parent animated-hover">
<i class="menu-item-icon fa fa-search faa-burst fa-fw"></i> <br />
搜索
</a>
</li>
</ul>
<div class="site-search">
<div class="popup search-popup local-search-popup">
<div class="local-search-header clearfix">
<span class="search-icon">
<i class="fa fa-search"></i>
</span>
<span class="popup-btn-close">
<i class="fa fa-times-circle"></i>
</span>
<div class="local-search-input-wrapper">
<input autocomplete="off"
placeholder="搜索..." spellcheck="false"
type="text" id="local-search-input">
</div>
</div>
<div id="local-search-result"></div>
</div>
</div>
</nav>
</div>
</header>
<main id="main" class="main">
<div class="main-inner">
<div class="content-wrap">
<div id="content" class="content">
<div id="posts" class="posts-expand">
<article class="post post-type-normal" itemscope itemtype="http://schema.org/Article">
<div class="post-date" data-datetime="2020-08-27T23:26:50+08:00">
<div class="post-time-text">8月</div>
<div class="post-time-count">27</div>
<div class="text-desc">
<div class="date-text">更新于</div>
<div class="post-tiem">8月27</div>
<div class="post-year">2020</div>
</div>
</div>
<div class="post-badge">
<span class="post-category" >
<span itemprop="about" itemscope itemtype="http://schema.org/Thing">
<a href="/categories/JS/" itemprop="url" rel="index">
<span itemprop="name">JS</span>
</a>
</span>
</span>
</div>
<div class="post-block">
<link itemprop="mainEntityOfPage" href="http://mydearest.cn/prototype.html">
<span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
<meta itemprop="name" content="陈宇（cosyer）">
<meta itemprop="description" content="不去做的话永远也做不到。">
<meta itemprop="image" content="/images/avatar.jpg">
</span>
<span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization">
<meta itemprop="name" content="cosyer's Blog">
</span>
<header class="post-header">
<h2 class="post-title" itemprop="name headline">JavaScript深入之从原型到原型链</h2>
<div class="post-meta">
<span class="post-time">
<span class="post-meta-item-icon">
<i class="fa fa-calendar-o"></i>
</span>
<span class="post-meta-item-text">发表于</span>
<time title="发表于" itemprop="dateCreated datePublished" datetime="2018-06-12T19:47:24+08:00">
2018-06-12
</time>
</span>
<span id="/prototype.html" class="leancloud_visitors" data-flag-title="JavaScript深入之从原型到原型链">
<span class="post-meta-divider">|</span>
<span class="post-meta-item-icon">
<i class="fa fa-eye"></i>
</span>
<span class="post-meta-item-text">热度 </span>
<span class="leancloud-visitors-count"></span> ℃
</span>
<div class="post-wordcount">
<span class="post-meta-divider">|</span>
<span class="post-meta-item-icon">
<i class="fa fa-pencil-square-o"></i>
</span>
<span class="post-meta-item-text">字数统计：</span>
<span title="字数统计：">
2,765 (字)
</span>
<span class="post-meta-divider">|</span>
<span class="post-meta-item-icon">
<i class="fa fa-clock-o"></i>
</span>
<span class="post-meta-item-text">阅读时长：</span>
<span title="阅读时长：">
11 (分钟)
</span>
</div>
</div>
</header>
<div class="post-body" itemprop="articleBody">
<blockquote class="blockquote-center"><p>原型对象的用途是为每个实例对象存储共享的方法和属性，它仅仅是一个普通对象而已，仅有一份。</p>
</blockquote>
<p>每个对象都会在其内部初始化一个属性，就是prototype(原型)，当我们访问一个对象的属性时，
如果这个对象内部不存在这个属性，那么它就会去prototype里找这个属性，这个prototype又会有自己的prototype，于是就这样一直找下去，也就是我们平时所说的原型链的概念</p>
<ul>
<li>“prototype” 是什么？
prototype 是所有公共方法和属性的宿主，从祖先派生的“子”对象可以从使用祖先的方法和属性。</li>
</ul>
<p>原型是一个用于实现对象属性继承的对象。</p>
<h2 id="构造函数创建对象"><a href="#构造函数创建对象" class="headerlink" title="构造函数创建对象"></a>构造函数创建对象</h2><p>我们先使用构造函数创建一个对象：</p>
<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">Person</span>(<span class="params"></span>) </span>{}</span><br><span class="line"><span class="keyword">var</span> person = <span class="keyword">new</span> Person();</span><br><span class="line">person.name = <span class="string">"cosyer"</span>;</span><br><span class="line"><span class="built_in">console</span>.log(person.name); <span class="comment">// cosyer</span></span><br></pre></td></tr></table></figure>
<p>在这个例子中，Person 就是一个构造函数，我们使用 new 创建了一个实例对象 person。</p>
<hr>
<a id="more"></a>
<p>很简单吧，接下来进入正题：</p>
<h3 id="prototype"><a href="#prototype" class="headerlink" title="prototype"></a>prototype</h3><p>每个函数都有一个 prototype 属性，就是我们经常在各种例子中看到的那个 prototype ，比如：</p>
<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">Person</span>(<span class="params"></span>) </span>{}</span><br><span class="line"><span class="comment">// prototype是函数才会有的属性</span></span><br><span class="line">Person.prototype.name = <span class="string">"cosyer"</span>;</span><br><span class="line"><span class="keyword">var</span> person1 = <span class="keyword">new</span> Person();</span><br><span class="line"><span class="keyword">var</span> person2 = <span class="keyword">new</span> Person();</span><br><span class="line"><span class="built_in">console</span>.log(person1.name); <span class="comment">// cosyer</span></span><br><span class="line"><span class="built_in">console</span>.log(person2.name); <span class="comment">// cosyer</span></span><br></pre></td></tr></table></figure>
<p>那这个函数的 prototype 属性到底指向的是什么呢？是这个函数的原型吗？</p>
<p>其实，函数的 prototype 属性指向了一个对象，这个对象正是调用该构造函数而创建的实例的原型，也就是这个例子中的 person1 和 person2 的原型。</p>
<p>那什么是原型呢？你可以这样理解：每一个 JavaScript 对象(null 除外)在创建的时候就会与之关联另一个对象，这个对象就是我们所说的原型，每一个对象都会从原型”继承”属性。</p>
<p>让我们用一张图表示构造函数和实例原型之间的关系：
<img src="http://cdn.mydearest.cn/blog/images/prototype1.png" alt="prototype"></p>
<p>在这张图中我们用 Object.prototype 表示实例原型。</p>
<p>那么我们该怎么表示实例与实例原型，也就是 person 和 Person.prototype 之间的关系呢，这时候我们就要讲到第二个属性：</p>
<h3 id="proto"><a href="#proto" class="headerlink" title="proto"></a><strong>proto</strong></h3><p>为了证明这一点,我们可以在火狐或者谷歌中输入：</p>
<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">Person</span>(<span class="params"></span>) </span>{}</span><br><span class="line"><span class="keyword">var</span> person = <span class="keyword">new</span> Person();</span><br><span class="line"><span class="built_in">console</span>.log(person.__proto__ === Person.prototype); <span class="comment">// true</span></span><br></pre></td></tr></table></figure>
<p>于是我们更新下关系图：
<img src="http://cdn.mydearest.cn/blog/images/prototype2.png" alt="prototype"></p>
<p>既然实例对象和构造函数都可以指向原型，那么原型是否有属性指向构造函数或者实例呢？</p>
<blockquote>
<p><strong>proto</strong>标准是浏览器实现的。</p>
</blockquote>
<h3 id="constructor-NaN"><a href="#constructor-NaN" class="headerlink" title="constructor"></a>constructor</h3><p>指向实例倒是没有，因为一个构造函数可以生成多个实例，但是原型指向构造函数倒是有的，这就要讲到第三个属性：constructor，每个原型都有一个 constructor 属性指向关联的构造函数。</p>
<p>为了验证这一点，我们可以尝试：</p>
<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">Person</span>(<span class="params"></span>) </span>{}</span><br><span class="line"><span class="built_in">console</span>.log(Person === Person.prototype.constructor); <span class="comment">// true</span></span><br></pre></td></tr></table></figure>
<p>所以再更新下关系图：
<img src="http://cdn.mydearest.cn/blog/images/prototype3.png" alt="prototype">
综上我们可以得出：</p>
<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">Person</span>(<span class="params"></span>) </span>{}</span><br><span class="line"></span><br><span class="line"><span class="keyword">var</span> person = <span class="keyword">new</span> Person();</span><br><span class="line"></span><br><span class="line"><span class="built_in">console</span>.log(person.__proto__ == Person.prototype); <span class="comment">// true</span></span><br><span class="line"><span class="built_in">console</span>.log(Person.prototype.constructor == Person); <span class="comment">// true</span></span><br><span class="line"><span class="comment">// 顺便学习一个ES5的方法,可以获得对象的原型 实例原型的constructor指向构造函数,构造函数的prototype指向实例原型,实例对象的__proto__指向实例原型,实例原型也是对象,它也有原型 最后的一个环节是null。访问实例对象的constructor时,也能从实例原型上去找,从而指向到构造函数。是一个用来实现继承和共享属性的有限的对象链。</span></span><br><span class="line"><span class="built_in">console</span>.log(<span class="built_in">Object</span>.getPrototypeOf(person) === Person.prototype); <span class="comment">// true</span></span><br></pre></td></tr></table></figure>
<h2 id="实例与原型"><a href="#实例与原型" class="headerlink" title="实例与原型"></a>实例与原型</h2><p>当读取实例的属性时，如果找不到，就会查找与对象关联的原型中的属性，如果还查不到，就去找原型的原型，一直找到最顶层为止。</p>
<p>举个例子：</p>
<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">Person</span>(<span class="params"></span>) </span>{}</span><br><span class="line"></span><br><span class="line">Person.prototype.name = <span class="string">"cosyer"</span>;</span><br><span class="line"></span><br><span class="line"><span class="keyword">var</span> person = <span class="keyword">new</span> Person();</span><br><span class="line"></span><br><span class="line">person.name = <span class="string">"Daisy"</span>;</span><br><span class="line"><span class="built_in">console</span>.log(person.name); <span class="comment">// Daisy</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">delete</span> person.name;</span><br><span class="line"><span class="built_in">console</span>.log(person.name); <span class="comment">// cosyer</span></span><br></pre></td></tr></table></figure>
<p>在这个例子中，我们给实例对象 person 添加了 name 属性，当我们打印 person.name 的时候，结果自然为 Daisy。</p>
<p>但是当我们删除了 person 的 name 属性时，读取 person.name，从 person 对象中找不到 name 属性就会从 person 的原型也就是 person.__proto__ ，也就是 Person.prototype 中查找，幸运的是我们找到了 name 属性，结果为 cosyer。</p>
<p>但是万一还没有找到呢？原型的原型又是什么呢？</p>
<h2 id="原型的原型"><a href="#原型的原型" class="headerlink" title="原型的原型"></a>原型的原型</h2><p>在前面，我们已经讲了原型也是一个对象，既然是对象，我们就可以用最原始的方式创建它，那就是：</p>
<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> obj = <span class="keyword">new</span> <span class="built_in">Object</span>();</span><br><span class="line">obj.name = <span class="string">"cosyer"</span>;</span><br><span class="line"><span class="built_in">console</span>.log(obj.name); <span class="comment">// cosyer</span></span><br></pre></td></tr></table></figure>
<p>其实原型对象就是通过 Object 构造函数生成的，结合之前所讲，实例的 <strong>proto</strong> 指向构造函数的 prototype ，所以我们再更新下关系图：
<img src="http://cdn.mydearest.cn/blog/images/prototype4.png" alt="prototype"></p>
<h2 id="原型链"><a href="#原型链" class="headerlink" title="原型链"></a>原型链</h2><p>那 Object.prototype 的原型呢？</p>
<p>null，我们可以打印：</p>
<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="built_in">console</span>.log(<span class="built_in">Object</span>.prototype.__proto__ === <span class="literal">null</span>); <span class="comment">// true</span></span><br></pre></td></tr></table></figure>
<p>然而 null 究竟代表了什么呢？</p>
<p>引用阮一峰老师的 《undefined 与 null 的区别》 就是：</p>
<p>null 表示“没有对象”，即该处不应该有值。</p>
<p>所以 Object.prototype.<strong>proto</strong> 的值为 null 跟 Object.prototype 没有原型，其实表达了一个意思。</p>
<p>所以查找属性的时候查到 Object.prototype 就可以停止查找了。</p>
<p>最后一张关系图也可以更新为：
<img src="http://cdn.mydearest.cn/blog/images/prototype5.png" alt="prototype"></p>
<p>图中由相互关联的原型组成的链状结构就是原型链，也就是蓝色的这条线。</p>
<h2 id="补充"><a href="#补充" class="headerlink" title="补充"></a>补充</h2><h3 id="constructor"><a href="#constructor" class="headerlink" title="constructor"></a>constructor</h3><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">Person</span>(<span class="params"></span>) </span>{}</span><br><span class="line"><span class="keyword">var</span> person = <span class="keyword">new</span> Person();</span><br><span class="line"><span class="built_in">console</span>.log(person.constructor === Person); <span class="comment">// true</span></span><br></pre></td></tr></table></figure>
<p>当获取 person.constructor 时，其实 person 中并没有 constructor 属性,当不能读取到 constructor 属性时，会从 person 的原型也就是 Person.prototype 中读取，正好原型中有该属性，所以：</p>
<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">person.constructor === Person.prototype.constructor;</span><br></pre></td></tr></table></figure>
<h3 id="proto-1"><a href="#proto-1" class="headerlink" title="proto"></a><strong>proto</strong></h3><p>其次是 <strong>proto</strong> ，绝大部分浏览器都支持这个非标准的方法访问原型，然而它并不存在于 Person.prototype 中，实际上，它是来自于 Object.prototype ，与其说是一个属性，不如说是一个 getter/setter，当使用 obj.<strong>proto</strong> 时，可以理解成返回了 Object.getPrototypeOf(obj)。</p>
<h3 id="继承"><a href="#继承" class="headerlink" title="继承"></a>继承</h3><p>最后是关于继承，前面我们讲到“每一个对象都会从原型‘继承’属性”，实际上，继承是一个十分具有迷惑性的说法，引用《你不知道的 JavaScript》中的话，就是：继承意味着复制操作，然而 JavaScript 默认并不会复制对象的属性，相反，JavaScript 只是在两个对象之间创建一个关联，这样，一个对象就可以通过委托访问另一个对象的属性和函数，所以与其叫继承，委托的说法反而更准确些。</p>
<ul>
<li>class 的引入只是语法糖本身还是基于原型的</li>
<li>几乎所有 JavaScript 中的对象都是位于原型链顶端的Object的实例。</li>
</ul>
<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Cat</span> </span>{</span><br><span class="line"> say() {</span><br><span class="line"> <span class="built_in">console</span>.log(<span class="string">"meow ~"</span>);</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">// 等价于</span></span><br><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">Cat</span>(<span class="params"></span>) </span>{}</span><br><span class="line"><span class="built_in">Object</span>.defineProperty(Cat.prototype, <span class="string">"say"</span>, {</span><br><span class="line"> value: <span class="function"><span class="keyword">function</span>(<span class="params"></span>) </span>{ <span class="built_in">console</span>.log(<span class="string">"meow ~"</span>); },</span><br><span class="line"> enumerable: <span class="literal">false</span>,</span><br><span class="line"> configurable: <span class="literal">true</span>,</span><br><span class="line"> writable: <span class="literal">true</span></span><br><span class="line">});</span><br><span class="line"></span><br><span class="line"><span class="comment">// es6 class是没有静态属性的 只有静态方法</span></span><br><span class="line"><span class="keyword">var</span> cat = <span class="keyword">new</span> Cat();</span><br><span class="line">cat.say(); <span class="comment">// meow~</span></span><br><span class="line">Cat.say(); <span class="comment">// error 加上static修饰正确 </span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 注解</span></span><br><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">isAnimal</span>(<span class="params">target</span>) </span>{</span><br><span class="line"> target.isAnimal = <span class="literal">true</span>;</span><br><span class="line"> <span class="keyword">return</span> target;</span><br><span class="line">}</span><br><span class="line">@isAnimal</span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Cat</span> </span>{</span><br><span class="line"> ...</span><br><span class="line">}</span><br><span class="line"><span class="comment">// 等价于</span></span><br><span class="line">Cat=isAnimal(<span class="function"><span class="keyword">function</span> <span class="title">Cat</span>(<span class="params"></span>)</span>{})</span><br><span class="line"></span><br><span class="line"><span class="built_in">console</span>.log(Cat.isAnimal); <span class="comment">// true</span></span><br></pre></td></tr></table></figure>
<h3 id="描述符"><a href="#描述符" class="headerlink" title="描述符"></a>描述符</h3><ul>
<li><p>Configurable 特性
configurable 特性表示对象的属性是否可以被删除，以及除 writable 特性外的其他特性是否可以被修改。</p>
</li>
<li><p>Enumerable 特性
属性特性 enumerable 定义了对象的属性是否可以在 for…in 循环和 Object.keys() 中被枚举。</p>
</li>
<li><p>Writable 属性
当属性特性（property attribute） writable 设置为false时，表示 non-writable，属性不能被修改。</p>
</li>
</ul>
<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> p = <span class="built_in">Object</span>.create(o);</span><br><span class="line"><span class="comment">// p是一个继承自 o 的对象</span></span><br><span class="line">对象的原型链</span><br><span class="line">o===><span class="built_in">Object</span>.prototype===><span class="literal">null</span></span><br><span class="line">数组的原型链</span><br><span class="line">a===><span class="built_in">Array</span>.prototype===><span class="built_in">Object</span>.prototype===><span class="literal">null</span></span><br><span class="line">函数的原型链</span><br><span class="line">f===><span class="built_in">Function</span>.prototype===><span class="built_in">Object</span>.prototype===><span class="literal">null</span></span><br><span class="line"></span><br><span class="line"><span class="built_in">Function</span>.__proto__==<span class="built_in">Object</span>.prototype <span class="comment">// false</span></span><br><span class="line"><span class="built_in">Function</span>.__proto__==<span class="built_in">Function</span>.prototype <span class="comment">// true Function的原型也是Function</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">var</span> Tom = <span class="built_in">Object</span>.create(Person, {</span><br><span class="line"> age: {</span><br><span class="line"> value: <span class="number">34</span>,</span><br><span class="line"> enumerable: <span class="literal">true</span>,</span><br><span class="line"> writable: <span class="literal">true</span>,</span><br><span class="line"> configurable: <span class="literal">true</span></span><br><span class="line"> },</span><br><span class="line"> name: {</span><br><span class="line"> value: <span class="string">"Tom"</span>,</span><br><span class="line"> enumerable: <span class="literal">true</span>,</span><br><span class="line"> writable: <span class="literal">true</span>,</span><br><span class="line"> configurable: <span class="literal">true</span></span><br><span class="line"> }</span><br><span class="line">});</span><br><span class="line"><span class="comment">// 以这种方式配置的属性默认情况下不可写，不可枚举，不可配置。 不可写意味着之后无法更改该属性，更改会被忽略。</span></span><br></pre></td></tr></table></figure>
<h3 id="原型对象的添加属性"><a href="#原型对象的添加属性" class="headerlink" title="原型对象的添加属性"></a>原型对象的添加属性</h3><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">Persion</span>(<span class="params"></span>)</span>{}</span><br><span class="line">Persion.prototype.sayName=<span class="function"><span class="keyword">function</span>(<span class="params"></span>)</span>{</span><br><span class="line"> <span class="built_in">console</span>.log(<span class="string">'darling'</span>)</span><br><span class="line">}</span><br><span class="line"><span class="comment">// Persion.prototype={</span></span><br><span class="line"><span class="comment">// sayName:function(){</span></span><br><span class="line"><span class="comment">// console.log('darling')</span></span><br><span class="line"><span class="comment">// } </span></span><br><span class="line"><span class="comment">// }</span></span><br><span class="line"><span class="keyword">let</span> persion =<span class="keyword">new</span> Persion()</span><br><span class="line">persion.sayName() <span class="comment">// darling</span></span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">Persion</span>(<span class="params"></span>)</span>{}</span><br><span class="line"><span class="keyword">let</span> persion=<span class="keyword">new</span> Persion()</span><br><span class="line"><span class="comment">// 这里重写了原型对象，实例对象和最初的原型对象断开了联系</span></span><br><span class="line"><span class="comment">// persion的proto指向一个空对象</span></span><br><span class="line">Persion.prototype={</span><br><span class="line"> sayName:<span class="function"><span class="keyword">function</span>(<span class="params"></span>)</span>{</span><br><span class="line"> <span class="built_in">console</span>.log(<span class="string">'darling'</span>)</span><br><span class="line"> } </span><br><span class="line">}</span><br><span class="line">persion.sayName() <span class="comment">// error</span></span><br></pre></td></tr></table></figure>
<h3 id="new-操作符具体干了什么"><a href="#new-操作符具体干了什么" class="headerlink" title="new 操作符具体干了什么"></a>new 操作符具体干了什么</h3><ol>
<li>创建空对象，并且this变量引用该对象同时继承该函数的原型</li>
<li>属性和方法加入到this引用的对象中</li>
<li><p>新创建的对象用this引用，并且隐式地返回this</p>
</li>
<li><p>创建一个新对象(__proto__ 指向构造函数的prototype)</p>
</li>
<li>把作用域（this）指给这个对象</li>
<li>执行构造函数的代码</li>
<li>如果构造函数中没有返回其它对象，那么返回 this，即创建的这个的新对象，否则，返回构造函数中返回的对象</li>
</ol>
<figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">Base</span>(<span class="params"></span>)</span>{</span><br><span class="line"> <span class="keyword">this</span>.id = <span class="string">"base"</span>;</span><br><span class="line">}</span><br><span class="line"><span class="keyword">var</span> obj = <span class="keyword">new</span> Base();</span><br></pre></td></tr></table></figure>
<p><strong>new干了什么？</strong> </p>
<ol>
<li><p>var obj = {};</p>
</li>
<li><p>obj.__proto__ = Base.protptype;</p>
</li>
<li><p>Base.call(obj);</p>
</li>
</ol>
<ul>
<li>es5使用Object.create()来创建对象 new Object() 字面量写法{}
使用Object.create()是将对象继承到<strong>proto</strong>属性上，
Object.create(null)没有继承任何原型方法，也就是说它的原型链没有上一层。</li>
<li><p>es6使用class关键字</p>
</li>
<li><p>构造器就是普通的函数,new来作用称为构造方法(构造函数)</p>
</li>
<li><p>访问原型链会损耗性能,不存在的属性会遍历原型链直到最后一层</p>
</li>
<li><p>hasOwnProperty 是 JavaScript 中唯一处理属性并且不会遍历原型链的方法。通常在for in循环中使用。</p>
</li>
</ul>
<h3 id="实现-new-函数"><a href="#实现-new-函数" class="headerlink" title="实现 new 函数"></a>实现 new 函数</h3><figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">_new</span>(<span class="params">func</span>) </span>{</span><br><span class="line"> <span class="comment">// 第一步 创建新对象</span></span><br><span class="line"> <span class="keyword">let</span> obj= {}; </span><br><span class="line"> <span class="comment">// 第二步 空对象的_proto_指向了构造函数的prototype成员对象</span></span><br><span class="line"> obj.__proto__ = func.prototype;<span class="comment">//</span></span><br><span class="line"> <span class="comment">// 一二步合并就相当于 let obj=Object.create(func.prototype)</span></span><br><span class="line"></span><br><span class="line"> <span class="comment">// 第三步 使用apply调用构造器函数，属性和方法被添加到 this 引用的对象中</span></span><br><span class="line"> <span class="keyword">let</span> result = func.apply(obj);</span><br><span class="line"> <span class="keyword">if</span> (result && (<span class="keyword">typeof</span> (result) == <span class="string">"object"</span> || <span class="keyword">typeof</span> (result) == <span class="string">"function"</span>)) {</span><br><span class="line"> <span class="comment">// 如果构造函数执行的结果返回的是一个对象，那么返回这个对象</span></span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">// 如果构造函数返回的不是一个对象，返回创建的新对象</span></span><br><span class="line"> <span class="keyword">return</span> obj;</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
</div>
<div>
<div>
<div class="text-center line pages-end">
<span>本文结束<i class="fa fa-meh-o fa-fw"></i>感谢您的阅读</span>
</div>
</div>
</div>
<div>
<div class="my_post_copyright">
<script src="//cdn.bootcss.com/clipboard.js/1.5.10/clipboard.min.js"></script>
<!-- JS库 sweetalert 可修改路径 -->
<script type="text/javascript" src="https://cdn.staticfile.org/jquery/1.7.1/jquery.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/sweetalert@1.0.0/dist/sweetalert.min.js"></script>
<link rel="stylesheet" type="text/css" href="https://cdn.jsdelivr.net/npm/sweetalert@1.0.0/dist/sweetalert.css">
<p><span>本文标题:</span><a href="/prototype.html">JavaScript深入之从原型到原型链</a></p>
<p><span>文章作者:</span><a href="/" title="访问 陈宇（cosyer） 的个人博客">陈宇（cosyer）</a></p>
<p><span>发布时间:</span>2018年06月12日 - 19:06</p>
<p><span>最后更新:</span>2020年08月27日 - 23:08</p>
<p><span>原始链接:</span><a href="/prototype.html" title="JavaScript深入之从原型到原型链">http://mydearest.cn/prototype.html</a>
<span class="copy-path" title="点击复制文章链接"><i class="fa fa-clipboard" data-clipboard-text="http://mydearest.cn/prototype.html" aria-label=" 复制成功！"></i></span>
</p>
<p><span>许可协议:</span><i class="fa fa-creative-commons"></i> <a rel="license" href="https://creativecommons.org/licenses/by-nc-nd/4.0/" target="_blank" title="Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)">署名-非商业性使用-禁止演绎 4.0 国际</a> 转载请保留原文链接及作者。</p>
</div>
<script>
var clipboard = new Clipboard('.fa-clipboard');
clipboard.on('success', $(function(){
$(".fa-clipboard").click(function(){
swal({
title: "",
text: '复制成功',
timer: 500,
showConfirmButton: false
});
});
}));
</script>
</div>
<div>
<div style="padding: 10px 0; margin: 20px auto; width: 90%; text-align: center;">
<div>坚持原创技术分享，您的支持将鼓励我继续创作！</div>
<button id="rewardButton" disable="enable" onclick="var qr = document.getElementById('QR'); if (qr.style.display === 'none') {qr.style.display='block';} else {qr.style.display='none'}">
<span>赏</span>
</button>
<div id="QR" style="display: none;">
<div id="wechat" style="display: inline-block">
<img id="wechat_qr" src="/images/wechatpay.png" alt="陈宇（cosyer） WeChat Pay"/>
<p>WeChat Pay</p>
</div>
<div id="alipay" style="display: inline-block">
<img id="alipay_qr" src="/images/alipay.png" alt="陈宇（cosyer） Alipay"/>
<p>Alipay</p>
</div>
</div>
</div>
</div>
<footer class="post-footer">
<div class="post-tags">
<a href="/tags/%E5%8E%9F%E5%9E%8B%E9%93%BE/" rel="tag"><i class="fa fa-tag fa-fw"></i> 原型链</a>
</div>
<div class="post-nav">
<div class="post-nav-next post-nav-item">
<a href="/smallknowledge.html" rel="next" title="你所不知道的前端冷门小知识(长期更新)">
<i class="fa fa-chevron-left"></i> 你所不知道的前端冷门小知识(长期更新)
</a>
</div>
<span class="post-nav-divider"></span>
<div class="post-nav-prev post-nav-item">
<a href="/scope.html" rel="prev" title="JavaScript深入之作用域">
JavaScript深入之作用域 <i class="fa fa-chevron-right"></i>
</a>
</div>
</div>
</footer>
</div>
</article>
<div class="post-spread">
</div>
</div>
</div>
<div class="comments" id="comments">
<div class="comments v" id="comments"></div>
</div>
</div>
<div class="sidebar-toggle">
<div class="sidebar-toggle-line-wrap">
<span class="sidebar-toggle-line sidebar-toggle-line-first"></span>
<span class="sidebar-toggle-line sidebar-toggle-line-middle"></span>
<span class="sidebar-toggle-line sidebar-toggle-line-last"></span>
</div>
</div>
<aside id="sidebar" class="sidebar">
<div class="sidebar-inner">
<ul class="sidebar-nav motion-element">
<li class="sidebar-nav-toc sidebar-nav-active" data-target="post-toc-wrap" >
文章目录
</li>
<li class="sidebar-nav-overview" data-target="site-overview">
站点概览
</li>
</ul>
<section class="site-overview sidebar-panel">
<div class="site-author motion-element" itemprop="author" itemscope itemtype="http://schema.org/Person">
<img class="site-author-image" itemprop="image"
src="/images/avatar.jpg"
alt="陈宇（cosyer）" />
<p class="site-author-name" itemprop="name">陈宇（cosyer）</p>
<p class="site-description motion-element" itemprop="description">不去做的话永远也做不到。</p>
</div>
<nav class="site-state motion-element">
<div class="site-state-item site-state-posts">
<a href="/archives/">
<span class="site-state-item-count">159</span>
<span class="site-state-item-name">日志</span>
</a>
</div>
<div class="site-state-item site-state-categories">
<a href="/categories/index.html">
<span class="site-state-item-count">10</span>
<span class="site-state-item-name">分类</span>
</a>
</div>
<div class="site-state-item site-state-tags">
<a href="/tags/index.html">
<span class="site-state-item-count">51</span>
<span class="site-state-item-name">标签</span>
</a>
</div>
</nav>
<div class="feed-link motion-element">
<a href="/rss2.xml" rel="alternate">
<i class="fa fa-rss"></i>
RSS
</a>
</div>
<div class="links-of-author motion-element">
<span class="links-of-author-item">
<a rel="external nofollow" href="https://github.com/cosyer" target="_blank" title="GitHub">
<i class="fa fa-fw fa-github"></i>
GitHub
</a>
</span>
<span class="links-of-author-item">
<a rel="external nofollow" href="https://twitter.com/yzchenyu1995" target="_blank" title="Twitter">
<i class="fa fa-fw fa-twitter"></i>
Twitter
</a>
</span>
<span class="links-of-author-item">
<a rel="external nofollow" href="mailto:yzchenyu1995@gmail.com" target="_blank" title="E-Mail">
<i class="fa fa-fw fa-envelope"></i>
E-Mail
</a>
</span>
<span class="links-of-author-item">
<a rel="external nofollow" href="https://www.facebook.com/profile.php?id=100025666071215" target="_blank" title="FB Page">
<i class="fa fa-fw fa-facebook"></i>
FB Page
</a>
</span>
</div>
<div class="links-of-blogroll motion-element links-of-blogroll-inline">
<div class="links-of-blogroll-title">
<i class="fa fa-fw fa-globe"></i>
推荐阅读
</div>
<ul class="links-of-blogroll-list">
<li class="links-of-blogroll-item">
<a rel="external nofollow" href="http://callmesoul.cn" title="Callmesoul" target="_blank">Callmesoul</a>
</li>
<li class="links-of-blogroll-item">
<a rel="external nofollow" href="https://www.jstips.co/" title="JsTips" target="_blank">JsTips</a>
</li>
<li class="links-of-blogroll-item">
<a rel="external nofollow" href="http://dir.mydearest.cn/motion/" title="Personal Site" target="_blank">Personal Site</a>
</li>
<li class="links-of-blogroll-item">
<a rel="external nofollow" href="http://resume.mydearest.cn/" title="Resume" target="_blank">Resume</a>