-
Notifications
You must be signed in to change notification settings - Fork 0
/
2019-01-12-深入JavaScript——执行上下文栈.html
1257 lines (682 loc) · 46.4 KB
/
2019-01-12-深入JavaScript——执行上下文栈.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
<!DOCTYPE html>
<html class="theme-next mist use-motion" lang="zh-Hans">
<head>
<meta charset="UTF-8"/>
<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">
<script src="/lib/pace/pace.min.js?v=1.0.2"></script>
<link href="/lib/pace/pace-theme-minimal.min.css?v=1.0.2" rel="stylesheet">
<meta http-equiv="Cache-Control" content="no-transform" />
<meta http-equiv="Cache-Control" content="no-siteapp" />
<link href="/lib/fancybox/source/jquery.fancybox.css?v=2.1.5" rel="stylesheet" type="text/css" />
<link href="/lib/font-awesome/css/font-awesome.min.css?v=4.6.2" rel="stylesheet" type="text/css" />
<link href="/css/main.css?v=5.1.4" rel="stylesheet" type="text/css" />
<link rel="apple-touch-icon" sizes="180x180" href="/images/apple-touch-icon-next.png?v=5.1.4">
<link rel="icon" type="image/png" sizes="32x32" href="/images/favicon-32x32-next.png?v=5.1.4">
<link rel="icon" type="image/png" sizes="16x16" href="/images/favicon-16x16-next.png?v=5.1.4">
<link rel="mask-icon" href="/images/logo.svg?v=5.1.4" color="#222">
<meta name="keywords" content="深入JavaScript," />
<link rel="alternate" href="/atom.xml" title="赖同学" type="application/atom+xml" />
<meta name="description" content="经一些热心网友推荐，看到了冴羽 的深入系列，现做学习与记录，希望可以每天学习一篇，加强巩固自己对于 js 的理解。原仓库地址。 JavaScript深入之执行上下文栈顺序执行举个例子： 12345678var foo = function()&#123; console.log('foo1');&#125;foo(); // foo1var foo = function()&#123;">
<meta name="keywords" content="深入JavaScript">
<meta property="og:type" content="article">
<meta property="og:title" content="深入JavaScript—— 执行上下文栈">
<meta property="og:url" content="http://laibh.top/2019-01-12-深入JavaScript——执行上下文栈.html">
<meta property="og:site_name" content="赖同学">
<meta property="og:description" content="经一些热心网友推荐，看到了冴羽 的深入系列，现做学习与记录，希望可以每天学习一篇，加强巩固自己对于 js 的理解。原仓库地址。 JavaScript深入之执行上下文栈顺序执行举个例子： 12345678var foo = function()&#123; console.log('foo1');&#125;foo(); // foo1var foo = function()&#123;">
<meta property="og:locale" content="zh-Hans">
<meta property="og:updated_time" content="2022-03-04T10:00:38.460Z">
<meta name="twitter:card" content="summary">
<meta name="twitter:title" content="深入JavaScript—— 执行上下文栈">
<meta name="twitter:description" content="经一些热心网友推荐，看到了冴羽 的深入系列，现做学习与记录，希望可以每天学习一篇，加强巩固自己对于 js 的理解。原仓库地址。 JavaScript深入之执行上下文栈顺序执行举个例子： 12345678var foo = function()&#123; console.log('foo1');&#125;foo(); // foo1var foo = function()&#123;">
<script type="text/javascript" id="hexo.configurations">
var NexT = window.NexT || {};
var CONFIG = {
root: '/',
scheme: 'Mist',
version: '5.1.4',
sidebar: {"position":"left","display":"post","offset":12,"b2t":false,"scrollpercent":true,"onmobile":false},
fancybox: true,
tabs: true,
motion: {"enable":true,"async":false,"transition":{"post_block":"fadeIn","post_header":"slideDownIn","post_body":"slideDownIn","coll_header":"slideLeftIn","sidebar":"slideUpIn"}},
duoshuo: {
userId: '0',
author: '博主'
},
algolia: {
applicationID: '1YNH8Y3MP9',
apiKey: '61c189facf700193dfcbb902369ce227',
indexName: 'MyBlog',
hits: {"per_page":10},
labels: {"input_placeholder":"想要找些什么呢","hits_empty":"${query} 没有被找到，再试试","hits_stats":"在 ${time} ms 查找了${hits}个结果"}
}
};
</script>
<link rel="canonical" href="http://laibh.top/2019-01-12-深入JavaScript——执行上下文栈.html"/>
<title>深入JavaScript—— 执行上下文栈 | 赖同学</title>
</head>
<body itemscope itemtype="http://schema.org/WebPage" lang="zh-Hans">
<div class="container sidebar-position-left page-post-detail">
<div class="headband"></div>
<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">赖同学</span>
<span class="logo-line-after"><i></i></span>
</a>
</div>
<h1 class="site-subtitle" itemprop="description"></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="/" rel="section">
<i class="menu-item-icon fa fa-fw fa-home"></i> <br />
首页
</a>
</li>
<li class="menu-item menu-item-tags">
<a href="/tags/" rel="section">
<i class="menu-item-icon fa fa-fw fa-tags"></i> <br />
标签
</a>
</li>
<li class="menu-item menu-item-categories">
<a href="/categories/" rel="section">
<i class="menu-item-icon fa fa-fw fa-th"></i> <br />
分类
</a>
</li>
<li class="menu-item menu-item-archives">
<a href="/archives/" rel="section">
<i class="menu-item-icon fa fa-fw fa-archive"></i> <br />
归档
</a>
</li>
<li class="menu-item menu-item-sitemap">
<a href="/sitemap.xml" rel="section">
<i class="menu-item-icon fa fa-fw fa-sitemap"></i> <br />
站点地图
</a>
</li>
<li class="menu-item menu-item-guestbook">
<a href="/guestbook" rel="section">
<i class="menu-item-icon fa fa-fw fa-comment"></i> <br />
留言
</a>
</li>
<li class="menu-item menu-item-search">
<a href="javascript:;" class="popup-trigger">
<i class="menu-item-icon fa fa-search fa-fw"></i> <br />
搜索
</a>
</li>
</ul>
<div class="site-search">
<div class="algolia-popup popup search-popup">
<div class="algolia-search">
<div class="algolia-search-input-icon">
<i class="fa fa-search"></i>
</div>
<div class="algolia-search-input" id="algolia-search-input"></div>
</div>
<div class="algolia-results">
<div id="algolia-stats"></div>
<div id="algolia-hits"></div>
<div id="algolia-pagination" class="algolia-pagination"></div>
</div>
<span class="popup-btn-close">
<i class="fa fa-times-circle"></i>
</span>
</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-block">
<link itemprop="mainEntityOfPage" href="http://laibh.top/2019-01-12-深入JavaScript——执行上下文栈.html">
<span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
<meta itemprop="name" content="赖彬鸿">
<meta itemprop="description" content="">
<meta itemprop="image" content="/images/myPhoto.jpg">
</span>
<span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization">
<meta itemprop="name" content="赖同学">
</span>
<header class="post-header">
<h2 class="post-title" itemprop="name headline">深入JavaScript—— 执行上下文栈</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="创建于" itemprop="dateCreated datePublished" datetime="2019-01-12T11:30:00+08:00">
2019-01-12
</time>
<span class="post-meta-divider">|</span>
<span class="post-meta-item-icon">
<i class="fa fa-calendar-check-o"></i>
</span>
<span class="post-meta-item-text">更新于:</span>
<time title="更新于" itemprop="dateModified" datetime="2022-03-04T18:00:38+08:00">
2022-03-04
</time>
</span>
<span class="post-category" >
<span class="post-meta-divider">|</span>
<span class="post-meta-item-icon">
<i class="fa fa-folder-o"></i>
</span>
<span class="post-meta-item-text">分类于</span>
<span itemprop="about" itemscope itemtype="http://schema.org/Thing">
<a href="/categories/JavaScript/" itemprop="url" rel="index">
<span itemprop="name">JavaScript</span>
</a>
</span>
</span>
<span id="/2019-01-12-深入JavaScript——执行上下文栈.html" class="leancloud_visitors" data-flag-title="深入JavaScript—— 执行上下文栈">
<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">阅读次数:</span>
<span class="leancloud-visitors-count"></span>
</span>
<div class="post-wordcount">
<span class="post-meta-item-icon">
<i class="fa fa-file-word-o"></i>
</span>
<span class="post-meta-item-text">字数统计:</span>
<span title="字数统计">
763
</span>
</div>
</div>
</header>
<div class="post-body" itemprop="articleBody">
<p>经一些热心网友推荐，看到了<a href="https://github.com/mqyqingfeng">冴羽</a> 的深入系列，现做学习与记录，希望可以每天学习一篇，加强巩固自己对于 js 的理解。<a href="https://github.com/mqyqingfeng/Blog">原仓库地址</a>。</p>
<h1 id="JavaScript深入之执行上下文栈"><a href="#JavaScript深入之执行上下文栈" class="headerlink" title="JavaScript深入之执行上下文栈"></a>JavaScript深入之执行上下文栈</h1><h2 id="顺序执行"><a href="#顺序执行" class="headerlink" title="顺序执行"></a>顺序执行</h2><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></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> foo = <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">'foo1'</span>);</span><br><span class="line">}</span><br><span class="line">foo(); <span class="comment">// foo1</span></span><br><span class="line"><span class="keyword">var</span> foo = <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">'foo2'</span>);</span><br><span class="line">}</span><br><span class="line">foo(); <span class="comment">// foo2</span></span><br></pre></td></tr></table></figure>
<p>另一个例子：</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></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> foo = <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">'foo1'</span>);</span><br><span class="line">}</span><br><span class="line">foo(); <span class="comment">// foo2</span></span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">foo</span>(<span class="params"></span>)</span>{</span><br><span class="line"> <span class="built_in">console</span>.log(<span class="string">'foo2'</span>);</span><br><span class="line">}</span><br><span class="line">foo(); <span class="comment">// foo2</span></span><br></pre></td></tr></table></figure>
<p>JavaScript 引擎并非一行一行地分析和执行程序的，而是一段一段分析执行。当执行一段代码的时候，会进行一个“准备工作”。比如第一个例子中的，变量提升。和第二个例子中的函数提升。</p>
<h2 id="可执行代码"><a href="#可执行代码" class="headerlink" title="可执行代码"></a>可执行代码</h2><p>分为三种：全局代码、函数代码和 eval 代码</p>
<p>举个例子。当执行到一个函数的时候，会进行准备工作，也就是我们经常听到的 “执行上下文（execution context）”</p>
<h2 id="执行上下文栈"><a href="#执行上下文栈" class="headerlink" title="执行上下文栈"></a>执行上下文栈</h2><p>JavaScript 引擎创建了执行上下文（Execution context stack,ECS）来管理执行上下文，为了模拟执行上下文栈的行为，让我们定义执行上下文是一个数组：</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">ECStack = [];</span><br></pre></td></tr></table></figure>
<p>当 JavaScript 开始要解释执行代码的时候，最先遇到的是全局代码，所以初始化的时候会首先向执行上下文栈压如一个全局执行上下文，我们用 globalContext 表示它，并且只有当整个应用程序结束的时候，ECStack 才会被清空，所以当程序结束之前，ECStack 最底部永远有一个 globalContext：</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">ECStack = [</span><br><span class="line"> globalContext</span><br><span class="line">]</span><br></pre></td></tr></table></figure>
<p>现在 JavaScript 遇到下面这段代码：</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></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">func3</span>(<span class="params"></span>)</span>{</span><br><span class="line"> <span class="built_in">console</span>.log(<span class="string">'func3'</span>);</span><br><span class="line">}</span><br><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">func2</span>(<span class="params"></span>)</span>{</span><br><span class="line"> func3();</span><br><span class="line">}</span><br><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">func1</span>(<span class="params"></span>)</span>{</span><br><span class="line"> func2();</span><br><span class="line">}</span><br><span class="line">func1();</span><br></pre></td></tr></table></figure>
<p>当执行一个函数的时候，就会创建一个上下文，并且压入执行上下文栈，当函数执行完毕的时候，就会将函数的执行上下文从栈中弹出，知道了这样的工作原理之后，让我们来看看如何处理上面这段代码：</p>
<figure class="highlight plain"><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></pre></td><td class="code"><pre><span class="line">// 伪代码</span><br><span class="line">// func1()</span><br><span class="line">ECStack.push(<func1> functionContext);</span><br><span class="line"></span><br><span class="line">// func1 中竟然调用了 func2，还要创建 func2 的执行上下文</span><br><span class="line">ECStack.push(<func2> functionContext);</span><br><span class="line"></span><br><span class="line">// func2 还调用了func3</span><br><span class="line">ECStack.push(<func3> functionContext);</span><br><span class="line"></span><br><span class="line">// func3 执行完毕</span><br><span class="line">ECStack.pop();</span><br><span class="line"></span><br><span class="line">// func2 执行完毕</span><br><span class="line">ECStack.pop();</span><br><span class="line"></span><br><span class="line">// func1 执行完毕</span><br><span class="line">ECStack.pop();</span><br><span class="line"></span><br><span class="line">// javascript 接着执行下面的代码，但是 ECStack 底层永远有个 globalContext</span><br></pre></td></tr></table></figure>
<h2 id="解答思考题"><a href="#解答思考题" class="headerlink" title="解答思考题"></a>解答思考题</h2><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></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">checkscope</span>(<span class="params"></span>)</span>{</span><br><span class="line"> <span class="keyword">var</span> scope = <span class="string">"local scope"</span>;</span><br><span class="line"> <span class="function"><span class="keyword">function</span> <span class="title">f</span>(<span class="params"></span>)</span>{</span><br><span class="line"> <span class="keyword">return</span> scope;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> f();</span><br><span class="line">}</span><br><span class="line">checkscope();</span><br><span class="line"></span><br><span class="line"><span class="keyword">var</span> scope = <span class="string">"global scope"</span>;</span><br><span class="line"><span class="function"><span class="keyword">function</span> <span class="title">checkscope</span>(<span class="params"></span>)</span>{</span><br><span class="line"> <span class="keyword">var</span> scope = <span class="string">"local scope"</span></span><br><span class="line"> <span class="function"><span class="keyword">function</span> <span class="title">f</span>(<span class="params"></span>)</span>{</span><br><span class="line"> <span class="keyword">return</span> scope;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> f;</span><br><span class="line">}</span><br><span class="line">checkscope()();</span><br></pre></td></tr></table></figure>
<p>两段代码不一样的地方主要体现在执行上下文栈的不一样</p>
<p>模拟第一段代码：</p>
<figure class="highlight plain"><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">ECStack.push(<checkscope> functionContext)</span><br><span class="line">ECStack.push(<f> functionContext)</span><br><span class="line">ECStack.pop();</span><br><span class="line">ECStack.pop();</span><br></pre></td></tr></table></figure>
<p>模拟第二段代码：</p>
<figure class="highlight plain"><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">ECStack.push(<checkscope> functionContext)</span><br><span class="line">ECStack.pop();</span><br><span class="line">ECStack.push(<f> functionContext)</span><br><span class="line">ECStack.pop();</span><br></pre></td></tr></table></figure>
</div>
<div>
<ul class="post-copyright">
<li class="post-copyright-author">
<strong>本文作者：</strong>
赖彬鸿
</li>
<li class="post-copyright-link">
<strong>本文链接：</strong>
<a href="http://laibh.top/2019-01-12-深入JavaScript——执行上下文栈.html" title="深入JavaScript—— 执行上下文栈">http://laibh.top/2019-01-12-深入JavaScript——执行上下文栈.html</a>
</li>
<li class="post-copyright-license">
<strong>版权声明： </strong>
本博客所有文章除特别声明外，均采用 <a href="https://creativecommons.org/licenses/by-nc-sa/3.0/" rel="external nofollow" target="_blank">CC BY-NC-SA 3.0</a> 许可协议。转载请注明出处！
</li>
</ul>
</div>
<footer class="post-footer">
<div class="post-tags">
<a href="/tags/深入JavaScript/" <i class="fa fa-tag"></i> 深入JavaScript</a>
</div>
<div class="post-nav">
<div class="post-nav-next post-nav-item">
<a href="/2019-01-11-深入JavaScript——作用域与动态作用域.html" rel="next" title="深入JavaScript—— 作用域与动态作用域">
<i class="fa fa-chevron-left"></i> 深入JavaScript—— 作用域与动态作用域
</a>
</div>
<span class="post-nav-divider"></span>
<div class="post-nav-prev post-nav-item">
<a href="/前端面试题目汇总摘录-JS 基础篇.html" rel="prev" title="前端面试题目汇总摘录（JS 基础篇）">
前端面试题目汇总摘录（JS 基础篇） <i class="fa fa-chevron-right"></i>
</a>
</div>
</div>
</footer>
</div>
</article>
<div class="post-spread">
<script>
window._bd_share_config = {
"common": {
"bdText": "",
"bdMini": "1",
"bdMiniList": false,
"bdPic": ""
},
"image": {
"viewList": ["tsina", "douban", "sqq", "qzone", "weixin", "twi", "fbook"],
"viewText": "分享到：",
"viewSize": "16"
},
"slide": {
"bdImg": "5",
"bdPos": "left",
"bdTop": "100"
}
}
</script>
<script>
with(document)0[(getElementsByTagName('head')[0]||body).appendChild(createElement('script')).src='/static/api/js/share.js?v=89860593.js?'+~(-new Date()/36e5)];;
</script>
</div>
</div>
</div>
<div class="comments" id="comments">
<div id="lv-container" data-id="city" data-uid="MTAyMC8zOTcwMy8xNjIzMA"></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-wrap">
站点概览
</li>
</ul>
<section class="site-overview-wrap sidebar-panel">
<div class="site-overview">
<div class="site-author motion-element" itemprop="author" itemscope itemtype="http://schema.org/Person">
<img class="site-author-image" itemprop="image"
src="/images/myPhoto.jpg"
alt="赖彬鸿" />
<p class="site-author-name" itemprop="name">赖彬鸿</p>
<p class="site-description motion-element" itemprop="description"></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">135</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">32</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">40</span>
<span class="site-state-item-name">标签</span>
</a>
</div>
</nav>
<div class="feed-link motion-element">
<a href="/atom.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 href="https://github.com/LbhFront-end" target="_blank" title="GitHub">
<i class="fa fa-fw fa-github"></i>GitHub</a>
</span>
<span class="links-of-author-item">
<a href="https://www.cnblogs.com/lbh2018/" target="_blank" title="博客园">
<i class="fa fa-fw fa-globe"></i>博客园</a>
</span>
<span class="links-of-author-item">
<a href="https://yq.aliyun.com/users/1802204154913774?spm=a2c4e.11153940.blogcont662526.4.6c0a34f6E2lR5o" target="_blank" title="云栖">
<i class="fa fa-fw fa-globe"></i>云栖</a>
</span>
<span class="links-of-author-item">
<a href="mailto:544289495@qq.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 href="tencent://AddContact/?fromId=45&fromSubId=1&subcmd=all&uin=544289495&website=www.oicqzone.com" target="_blank" title="QQ">
<i class="fa fa-fw fa-qq"></i>QQ</a>
</span>
<span class="links-of-author-item">
<a href="https://www.google.com.hk/search?safe=strict&source=hp&ei=JtLCXIriJ8G4-gS_-4qABQ&q=site%3Alaibh.top&btnK=Google+%E6%90%9C%E7%B4%A2&oq=site%3Alaibh.top&gs_l=psy-ab.3...1158.6834..7051...5.0..1.246.3720.2-17......0....1..gws-wiz.....0..0j0i10.rJMUHvdrbds" target="_blank" title="Google">
<i class="fa fa-fw fa-google"></i>Google</a>
</span>
</div>
<iframe frameborder="no" border="0" marginwidth="0" marginheight="0" width=330 height=90 src="//music.163.com/outchain/player?type=0&id=2353471182&auto=0&height=90"></iframe>
<div class="links-of-blogroll motion-element links-of-blogroll-inline">
<div class="links-of-blogroll-title">
<i class="fa fa-fw fa-link"></i>
友情链接
</div>
<ul class="links-of-blogroll-list">
<li class="links-of-blogroll-item">
<a href="http://www.chjtx.com/JRoll/" title="醉萝卜" target="_blank">醉萝卜</a>
</li>
<li class="links-of-blogroll-item">
<a href="http://hzd.plus/" title="Zhendong" target="_blank">Zhendong</a>
</li>
<li class="links-of-blogroll-item">
<a href="https://www.cnblogs.com/cnyball" title="cnyballk" target="_blank">cnyballk</a>
</li>
<li class="links-of-blogroll-item">
<a href="http://johnzz.top/" title="John" target="_blank">John</a>
</li>
<li class="links-of-blogroll-item">
<a href="https://xiaojun1994.top/" title="xiaojun1994" target="_blank">xiaojun1994</a>
</li>
<li class="links-of-blogroll-item">
<a href="https://me.ursb.me" title="Airing" target="_blank">Airing</a>
</li>
<li class="links-of-blogroll-item">
<a href="https://www.iyouhun.com" title="游魂" target="_blank">游魂</a>
</li>
<li class="links-of-blogroll-item">
<a href="https://icoty.github.io/" title="荒野之萍" target="_blank">荒野之萍</a>
</li>
<li class="links-of-blogroll-item">
<a href="https://im-one.github.io/" title="imOne" target="_blank">imOne</a>
</li>
<li class="links-of-blogroll-item">
<a href="http://blog.hourxu.com/" title="Ambre" target="_blank">Ambre</a>
</li>
<li class="links-of-blogroll-item">
<a href="http://www.huyujs.com" title="胡雨" target="_blank">胡雨</a>
</li>
<li class="links-of-blogroll-item">
<a href="https://www.andou.live" title="安逗" target="_blank">安逗</a>
</li>
<li class="links-of-blogroll-item">
<a href="https://www.jianshu.com/u/701a8bbf4f7e" title="陈健斌" target="_blank">陈健斌</a>
</li>
<li class="links-of-blogroll-item">
<a href="https://itobys.github.io/" title="汤姆Tom酱" target="_blank">汤姆Tom酱</a>
</li>
<li class="links-of-blogroll-item">
<a href="https://breeze2.github.io/blog/" title="林毅锋" target="_blank">林毅锋</a>
</li>
<li class="links-of-blogroll-item">
<a href="http://www.qzroc.com/" title="大鹏博客" target="_blank">大鹏博客</a>
</li>
<li class="links-of-blogroll-item">
<a href="https://lyreal666.com/" title="余腾靖的博客" target="_blank">余腾靖的博客</a>
</li>
<li class="links-of-blogroll-item">
<a href="https://buzuosheng.com/" title="不作声" target="_blank">不作声</a>
</li>
<li class="links-of-blogroll-item">
<a href="https://www.baidu.com/s?ie=UTF-8&wd=site%3Alaibh.top" title="百度" target="_blank">百度</a>
</li>
<li class="links-of-blogroll-item">
<a href="https://www.google.com.hk/search?safe=strict&source=hp&ei=zXdWXfemLJbO0PEP8qyXyA0&q=site%3Alaibh.top&oq=site%3Alaibh.top&gs_l=psy-ab.3...580.8501..8767...0.0..0.397.934.2-1j2......0....2j1..gws-wiz.QESXfWGadT0&ved=0ahUKEwi3wbusiofkAhUWJzQIHXLWBdkQ4dUDCAU&uact=5" title="谷歌" target="_blank">谷歌</a>
</li>
</ul>
</div>
</div>
</section>
<!--noindex-->
<section class="post-toc-wrap motion-element sidebar-panel sidebar-panel-active">
<div class="post-toc">
<div class="post-toc-content"><ol class="nav"><li class="nav-item nav-level-1"><a class="nav-link" href="#JavaScript深入之执行上下文栈"><span class="nav-number">1.</span> <span class="nav-text">JavaScript深入之执行上下文栈</span></a><ol class="nav-child"><li class="nav-item nav-level-2"><a class="nav-link" href="#顺序执行"><span class="nav-number">1.1.</span> <span class="nav-text">顺序执行</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#可执行代码"><span class="nav-number">1.2.</span> <span class="nav-text">可执行代码</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#执行上下文栈"><span class="nav-number">1.3.</span> <span class="nav-text">执行上下文栈</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#解答思考题"><span class="nav-number">1.4.</span> <span class="nav-text">解答思考题</span></a></li></ol></li></ol></div>
</div>
</section>
<!--/noindex-->
</div>
</aside>
</div>
</main>
<footer id="footer" class="footer">
<div class="footer-inner">
<script async src="//busuanzi.ibruce.info/busuanzi/2.3/busuanzi.pure.mini.js"></script>
<div class="copyright">© 2018 — <span itemprop="copyrightYear">2022</span>
<span class="with-love">
<i class="fa fa-heart throb" style="color: #d43f57;"></i>
</span>
<span class="author" itemprop="copyrightHolder">赖彬鸿</span>
</div>
<script src='https://unpkg.com/mermaid@7.1.2/dist/mermaid.min.js'></script>
<script>
if (window.mermaid) {
mermaid.initialize("");
}
</script>
<!--
<div class="powered-by">由 <a class="theme-link" target="_blank" href="https://hexo.io">Hexo</a> 强力驱动</div>
<span class="post-meta-divider">|</span>
<div class="theme-info">主题 — <a class="theme-link" target="_blank" href="https://github.com/iissnan/hexo-theme-next">NexT.Mist</a> v5.1.4</div>
-->
<div>
<span id="busuanzi_container_site_pv" title="访问量">
<i class="fa fa fa-eye"></i> <span id="busuanzi_value_site_pv"></span>
</span>
<span id="busuanzi_container_site_uv" title="访问人数">
<i class="fa fa-user"></i> <span id="busuanzi_value_site_uv"></span>
</span>
<span class="post-count" title="博客总字数"><i class="fa fa-pagelines" aria-hidden="true"></i>745.9k</span>
</div>
<i class="fa fa-shield" aria-hidden="true" title="本站安全运行时间"></i> <span id="timeDate">载入天数...</span><span id="times">载入时分秒...</span>
<script>
var now = new Date();
function createtime() {
var grt= new Date("01/29/2018 09:47:04");//此处修改你的建站时间或者网站上线时间
now.setTime(now.getTime()+250);
days = (now - grt ) / 1000 / 60 / 60 / 24; dnum = Math.floor(days);
hours = (now - grt ) / 1000 / 60 / 60 - (24 * dnum); hnum = Math.floor(hours);
if(String(hnum).length ==1 ){hnum = "0" + hnum;} minutes = (now - grt ) / 1000 /60 - (24 * 60 * dnum) - (60 * hnum);
mnum = Math.floor(minutes); if(String(mnum).length ==1 ){mnum = "0" + mnum;}
seconds = (now - grt ) / 1000 - (24 * 60 * 60 * dnum) - (60 * 60 * hnum) - (60 * mnum);
snum = Math.round(seconds);
if(String(snum).length ==1 ){snum = "0" + snum;}
document.getElementById("timeDate").innerHTML = dnum+" 天 ";
document.getElementById("times").innerHTML = hnum + " 小时 " + mnum + " 分 " + snum + " 秒";
}
setInterval("createtime()",250);
</script>
</div>
</footer>
<div class="back-to-top">
<i class="fa fa-arrow-up"></i>
<span id="scrollpercent"><span>0</span>%</span>
</div>
</div>
<script type="text/javascript">
if (Object.prototype.toString.call(window.Promise) !== '[object Function]') {
window.Promise = null;
}
</script>
<script type="text/javascript" src="//cdn.bootcss.com/jquery/2.1.3/jquery.min.js"></script>
<script type="text/javascript" src="/lib/fastclick/lib/fastclick.min.js?v=1.0.6"></script>
<script type="text/javascript" src="/lib/jquery_lazyload/jquery.lazyload.js?v=1.9.7"></script>
<script type="text/javascript" src="/lib/velocity/velocity.min.js?v=1.2.1"></script>
<script type="text/javascript" src="/lib/velocity/velocity.ui.min.js?v=1.2.1"></script>
<script type="text/javascript" src="/lib/fancybox/source/jquery.fancybox.pack.js?v=2.1.5"></script>