首页 发现 帮助
注册 登录
root
/
blog_web
1
0
派生 0
文件 工单管理 0 合并请求 0 Wiki
目录树: 749ca342c3
分支列表 标签列表
blog_web
/
pages
/
984bf549204bb266
/
index.html

index.html 108 KB
文件历史 原始文件

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323324325326327328329330331332333334335336337338339340341342343344345346347348349350351352353354355356357358359360361 
  1. <!DOCTYPE html>
    2. 

  2. <html lang="zh-CN">
    3. 

  3.   <head>
    4. 

  4.     <meta charset="utf-8">
    5. 

  5.     <meta name="viewport" content="width=device-width,initial-scale=1">
    6. 

  6.     <title>编程风格 | 彪哥博客</title>
    7. 

  7.     <meta name="generator" content="VuePress 1.9.5">
    8. 

  8.     <link rel="icon" href="/blog/img/favicon.ico">
    9. 

  9.     <meta name="description" content="web前端技术博客,专注web前端学习与总结。JavaScript,js,ES6,TypeScript,vue,React,python,css3,html5,Node,git,github等技术文章。">
    10. 

  10.     <meta name="keywords" content="前端博客,个人技术博客,前端,前端开发,前端框架,web前端,前端面试题,技术文档,学习,面试,JavaScript,js,ES6,TypeScript,vue,python,css3,html5,Node,git,github,markdown">
    11. 

  11.     <meta name="theme-color" content="#11a8cd">
    12. 

  12.     
    13. 

  13.     <link rel="preload" href="/blog/assets/css/0.styles.cf6c3304.css" as="style"><link rel="preload" href="/blog/assets/js/app.b419507c.js" as="script"><link rel="preload" href="/blog/assets/js/2.602aac03.js" as="script"><link rel="preload" href="/blog/assets/js/111.33bbfeaf.js" as="script"><link rel="prefetch" href="/blog/assets/js/10.05bc42d6.js"><link rel="prefetch" href="/blog/assets/js/100.93782085.js"><link rel="prefetch" href="/blog/assets/js/101.49f33592.js"><link rel="prefetch" href="/blog/assets/js/102.b391aaca.js"><link rel="prefetch" href="/blog/assets/js/103.b5c297df.js"><link rel="prefetch" href="/blog/assets/js/104.1b8956b0.js"><link rel="prefetch" href="/blog/assets/js/105.4af5ed2a.js"><link rel="prefetch" href="/blog/assets/js/106.f5ff0141.js"><link rel="prefetch" href="/blog/assets/js/107.9b0935ed.js"><link rel="prefetch" href="/blog/assets/js/108.a3b3e687.js"><link rel="prefetch" href="/blog/assets/js/109.0faeea62.js"><link rel="prefetch" href="/blog/assets/js/11.803b5050.js"><link rel="prefetch" href="/blog/assets/js/110.05696e77.js"><link rel="prefetch" href="/blog/assets/js/112.cc349461.js"><link rel="prefetch" href="/blog/assets/js/113.ee6a59a5.js"><link rel="prefetch" href="/blog/assets/js/114.837d6a71.js"><link rel="prefetch" href="/blog/assets/js/115.035a54c0.js"><link rel="prefetch" href="/blog/assets/js/116.bffbfdca.js"><link rel="prefetch" href="/blog/assets/js/117.effbf98c.js"><link rel="prefetch" href="/blog/assets/js/118.a2ce28a1.js"><link rel="prefetch" href="/blog/assets/js/119.da6e315d.js"><link rel="prefetch" href="/blog/assets/js/12.68f9aa15.js"><link rel="prefetch" href="/blog/assets/js/120.edc4f23e.js"><link rel="prefetch" href="/blog/assets/js/121.67388947.js"><link rel="prefetch" href="/blog/assets/js/122.0e892f37.js"><link rel="prefetch" href="/blog/assets/js/123.9c12e399.js"><link rel="prefetch" href="/blog/assets/js/124.e265d82a.js"><link rel="prefetch" href="/blog/assets/js/125.07ad81ea.js"><link rel="prefetch" href="/blog/assets/js/126.30be0256.js"><link rel="prefetch" href="/blog/assets/js/127.daf6f659.js"><link rel="prefetch" href="/blog/assets/js/128.c3aa5522.js"><link rel="prefetch" href="/blog/assets/js/129.60c2ac70.js"><link rel="prefetch" href="/blog/assets/js/13.b2f4726e.js"><link rel="prefetch" href="/blog/assets/js/130.283b36c2.js"><link rel="prefetch" href="/blog/assets/js/131.36fd29f9.js"><link rel="prefetch" href="/blog/assets/js/132.aa486fed.js"><link rel="prefetch" href="/blog/assets/js/133.5244b658.js"><link rel="prefetch" href="/blog/assets/js/134.5d546ce7.js"><link rel="prefetch" href="/blog/assets/js/135.efe5189e.js"><link rel="prefetch" href="/blog/assets/js/136.0e15e278.js"><link rel="prefetch" href="/blog/assets/js/137.9ed0177b.js"><link rel="prefetch" href="/blog/assets/js/138.0b8bc204.js"><link rel="prefetch" href="/blog/assets/js/139.cc005358.js"><link rel="prefetch" href="/blog/assets/js/14.8dc92978.js"><link rel="prefetch" href="/blog/assets/js/140.bc32a870.js"><link rel="prefetch" href="/blog/assets/js/141.acfd1af2.js"><link rel="prefetch" href="/blog/assets/js/142.4acb4dd6.js"><link rel="prefetch" href="/blog/assets/js/143.8182807e.js"><link rel="prefetch" href="/blog/assets/js/144.20a6c974.js"><link rel="prefetch" href="/blog/assets/js/145.f3a9911c.js"><link rel="prefetch" href="/blog/assets/js/146.3ed86675.js"><link rel="prefetch" href="/blog/assets/js/147.fa9b3898.js"><link rel="prefetch" href="/blog/assets/js/148.f498d3e2.js"><link rel="prefetch" href="/blog/assets/js/149.3fe441c6.js"><link rel="prefetch" href="/blog/assets/js/15.c32eb5e6.js"><link rel="prefetch" href="/blog/assets/js/150.6d73379d.js"><link rel="prefetch" href="/blog/assets/js/151.4916058e.js"><link rel="prefetch" href="/blog/assets/js/152.42f788ce.js"><link rel="prefetch" href="/blog/assets/js/153.57ac80e4.js"><link rel="prefetch" href="/blog/assets/js/154.46b3a2b3.js"><link rel="prefetch" href="/blog/assets/js/155.f16ed794.js"><link rel="prefetch" href="/blog/assets/js/156.7004ac8c.js"><link rel="prefetch" href="/blog/assets/js/157.54029a82.js"><link rel="prefetch" href="/blog/assets/js/158.d1a36e56.js"><link rel="prefetch" href="/blog/assets/js/159.e3aba89f.js"><link rel="prefetch" href="/blog/assets/js/16.ce96f674.js"><link rel="prefetch" href="/blog/assets/js/160.da511416.js"><link rel="prefetch" href="/blog/assets/js/161.e4fc79bf.js"><link rel="prefetch" href="/blog/assets/js/162.f214074e.js"><link rel="prefetch" href="/blog/assets/js/163.4bf1ce2d.js"><link rel="prefetch" href="/blog/assets/js/164.50c2a26a.js"><link rel="prefetch" href="/blog/assets/js/165.3fadd30d.js"><link rel="prefetch" href="/blog/assets/js/166.b46fceba.js"><link rel="prefetch" href="/blog/assets/js/167.6c6747d8.js"><link rel="prefetch" href="/blog/assets/js/168.87ccce63.js"><link rel="prefetch" href="/blog/assets/js/169.e1e1c58b.js"><link rel="prefetch" href="/blog/assets/js/17.a693fe7f.js"><link rel="prefetch" href="/blog/assets/js/170.755abdff.js"><link rel="prefetch" href="/blog/assets/js/171.a6b69067.js"><link rel="prefetch" href="/blog/assets/js/172.52c10d67.js"><link rel="prefetch" href="/blog/assets/js/173.568ec26d.js"><link rel="prefetch" href="/blog/assets/js/174.f6ff5c51.js"><link rel="prefetch" href="/blog/assets/js/175.f2d646a9.js"><link rel="prefetch" href="/blog/assets/js/176.2fd93f9c.js"><link rel="prefetch" href="/blog/assets/js/177.fc5683f6.js"><link rel="prefetch" href="/blog/assets/js/178.432e7e1f.js"><link rel="prefetch" href="/blog/assets/js/179.e63b01b0.js"><link rel="prefetch" href="/blog/assets/js/18.6df3c873.js"><link rel="prefetch" href="/blog/assets/js/180.7a136172.js"><link rel="prefetch" href="/blog/assets/js/181.6e78e56b.js"><link rel="prefetch" href="/blog/assets/js/182.73d2f94a.js"><link rel="prefetch" href="/blog/assets/js/183.dce8f42f.js"><link rel="prefetch" href="/blog/assets/js/184.94ec7685.js"><link rel="prefetch" href="/blog/assets/js/185.c3561080.js"><link rel="prefetch" href="/blog/assets/js/186.63b6c4b4.js"><link rel="prefetch" href="/blog/assets/js/187.b1ca4046.js"><link rel="prefetch" href="/blog/assets/js/188.6525cd10.js"><link rel="prefetch" href="/blog/assets/js/189.fdd57a16.js"><link rel="prefetch" href="/blog/assets/js/19.6ffd68ce.js"><link rel="prefetch" href="/blog/assets/js/190.8d9ac4f5.js"><link rel="prefetch" href="/blog/assets/js/191.f19beada.js"><link rel="prefetch" href="/blog/assets/js/192.bcd02302.js"><link rel="prefetch" href="/blog/assets/js/193.05afb721.js"><link rel="prefetch" href="/blog/assets/js/194.698e74d2.js"><link rel="prefetch" href="/blog/assets/js/195.70ee23b9.js"><link rel="prefetch" href="/blog/assets/js/196.14c12f32.js"><link rel="prefetch" href="/blog/assets/js/197.52e07cb7.js"><link rel="prefetch" href="/blog/assets/js/198.6312a976.js"><link rel="prefetch" href="/blog/assets/js/199.600b8211.js"><link rel="prefetch" href="/blog/assets/js/20.d994b814.js"><link rel="prefetch" href="/blog/assets/js/200.1658389e.js"><link rel="prefetch" href="/blog/assets/js/201.f2ecc5d4.js"><link rel="prefetch" href="/blog/assets/js/202.05a5bb1c.js"><link rel="prefetch" href="/blog/assets/js/203.893b83ad.js"><link rel="prefetch" href="/blog/assets/js/204.a90c3691.js"><link rel="prefetch" href="/blog/assets/js/205.d82fb971.js"><link rel="prefetch" href="/blog/assets/js/206.00e0b021.js"><link rel="prefetch" href="/blog/assets/js/207.a5dbb279.js"><link rel="prefetch" href="/blog/assets/js/208.d15bb006.js"><link rel="prefetch" href="/blog/assets/js/209.00d63e46.js"><link rel="prefetch" href="/blog/assets/js/21.2587b99c.js"><link rel="prefetch" href="/blog/assets/js/210.b256d7b8.js"><link rel="prefetch" href="/blog/assets/js/211.be264f59.js"><link rel="prefetch" href="/blog/assets/js/212.9956352d.js"><link rel="prefetch" href="/blog/assets/js/213.6144a981.js"><link rel="prefetch" href="/blog/assets/js/214.926fcb0b.js"><link rel="prefetch" href="/blog/assets/js/215.19148b26.js"><link rel="prefetch" href="/blog/assets/js/216.f56e94aa.js"><link rel="prefetch" href="/blog/assets/js/217.c5a75265.js"><link rel="prefetch" href="/blog/assets/js/218.1d08fa09.js"><link rel="prefetch" href="/blog/assets/js/219.11d14310.js"><link rel="prefetch" href="/blog/assets/js/22.cbb873e2.js"><link rel="prefetch" href="/blog/assets/js/220.31c10a26.js"><link rel="prefetch" href="/blog/assets/js/221.b95f8a68.js"><link rel="prefetch" href="/blog/assets/js/222.79b831b9.js"><link rel="prefetch" href="/blog/assets/js/223.23d684a8.js"><link rel="prefetch" href="/blog/assets/js/224.86b7a46d.js"><link rel="prefetch" href="/blog/assets/js/225.ba05abd3.js"><link rel="prefetch" href="/blog/assets/js/226.759b748e.js"><link rel="prefetch" href="/blog/assets/js/227.c26a7240.js"><link rel="prefetch" href="/blog/assets/js/228.de29829d.js"><link rel="prefetch" href="/blog/assets/js/229.83cf7341.js"><link rel="prefetch" href="/blog/assets/js/23.3392ec01.js"><link rel="prefetch" href="/blog/assets/js/230.d239ed00.js"><link rel="prefetch" href="/blog/assets/js/231.ddfd0758.js"><link rel="prefetch" href="/blog/assets/js/232.6b57acfb.js"><link rel="prefetch" href="/blog/assets/js/233.a104a750.js"><link rel="prefetch" href="/blog/assets/js/234.3d041b0e.js"><link rel="prefetch" href="/blog/assets/js/235.9e19c5d0.js"><link rel="prefetch" href="/blog/assets/js/236.9f300061.js"><link rel="prefetch" href="/blog/assets/js/237.9fb8d4bd.js"><link rel="prefetch" href="/blog/assets/js/238.ceec05fc.js"><link rel="prefetch" href="/blog/assets/js/24.736495d8.js"><link rel="prefetch" href="/blog/assets/js/25.8f5cf322.js"><link rel="prefetch" href="/blog/assets/js/26.67d8ecd5.js"><link rel="prefetch" href="/blog/assets/js/27.05800199.js"><link rel="prefetch" href="/blog/assets/js/28.72a4cebd.js"><link rel="prefetch" href="/blog/assets/js/29.f8d2f7c1.js"><link rel="prefetch" href="/blog/assets/js/3.aec45124.js"><link rel="prefetch" href="/blog/assets/js/30.0ac25def.js"><link rel="prefetch" href="/blog/assets/js/31.4d385616.js"><link rel="prefetch" href="/blog/assets/js/32.ab6922e1.js"><link rel="prefetch" href="/blog/assets/js/33.22aedb73.js"><link rel="prefetch" href="/blog/assets/js/34.1176b400.js"><link rel="prefetch" href="/blog/assets/js/35.d4d05428.js"><link rel="prefetch" href="/blog/assets/js/36.6dd0dde1.js"><link rel="prefetch" href="/blog/assets/js/37.4af0c50a.js"><link rel="prefetch" href="/blog/assets/js/38.1a98317a.js"><link rel="prefetch" href="/blog/assets/js/39.8383d231.js"><link rel="prefetch" href="/blog/assets/js/4.6a499ed7.js"><link rel="prefetch" href="/blog/assets/js/40.ea1ea46b.js"><link rel="prefetch" href="/blog/assets/js/41.29846640.js"><link rel="prefetch" href="/blog/assets/js/42.9c906181.js"><link rel="prefetch" href="/blog/assets/js/43.344bd56a.js"><link rel="prefetch" href="/blog/assets/js/44.e23af589.js"><link rel="prefetch" href="/blog/assets/js/45.fa09e088.js"><link rel="prefetch" href="/blog/assets/js/46.ddf18f6d.js"><link rel="prefetch" href="/blog/assets/js/47.593a3a96.js"><link rel="prefetch" href="/blog/assets/js/48.fb21c024.js"><link rel="prefetch" href="/blog/assets/js/49.5bb86e0c.js"><link rel="prefetch" href="/blog/assets/js/5.48f0d794.js"><link rel="prefetch" href="/blog/assets/js/50.0fb55bed.js"><link rel="prefetch" href="/blog/assets/js/51.a38b4abd.js"><link rel="prefetch" href="/blog/assets/js/52.70f6922c.js"><link rel="prefetch" href="/blog/assets/js/53.c7e04159.js"><link rel="prefetch" href="/blog/assets/js/54.ff09ad12.js"><link rel="prefetch" href="/blog/assets/js/55.57d17d47.js"><link rel="prefetch" href="/blog/assets/js/56.a58b3cc3.js"><link rel="prefetch" href="/blog/assets/js/57.9de5f95b.js"><link rel="prefetch" href="/blog/assets/js/58.d15857bf.js"><link rel="prefetch" href="/blog/assets/js/59.ff3f0900.js"><link rel="prefetch" href="/blog/assets/js/6.1505523f.js"><link rel="prefetch" href="/blog/assets/js/60.bc9edb0a.js"><link rel="prefetch" href="/blog/assets/js/61.ec369f58.js"><link rel="prefetch" href="/blog/assets/js/62.75c1dd19.js"><link rel="prefetch" href="/blog/assets/js/63.a932b576.js"><link rel="prefetch" href="/blog/assets/js/64.d821c8d4.js"><link rel="prefetch" href="/blog/assets/js/65.c48ce70a.js"><link rel="prefetch" href="/blog/assets/js/66.6fc46ec0.js"><link rel="prefetch" href="/blog/assets/js/67.5a70400c.js"><link rel="prefetch" href="/blog/assets/js/68.6a172c1e.js"><link rel="prefetch" href="/blog/assets/js/69.d878fdd4.js"><link rel="prefetch" href="/blog/assets/js/7.b38bde58.js"><link rel="prefetch" href="/blog/assets/js/70.61fcea39.js"><link rel="prefetch" href="/blog/assets/js/71.b4f867d8.js"><link rel="prefetch" href="/blog/assets/js/72.d6eafa00.js"><link rel="prefetch" href="/blog/assets/js/73.7937e89b.js"><link rel="prefetch" href="/blog/assets/js/74.3ff087d7.js"><link rel="prefetch" href="/blog/assets/js/75.97ca5f60.js"><link rel="prefetch" href="/blog/assets/js/76.ece1fc97.js"><link rel="prefetch" href="/blog/assets/js/77.95cdf309.js"><link rel="prefetch" href="/blog/assets/js/78.da225d8a.js"><link rel="prefetch" href="/blog/assets/js/79.ae629400.js"><link rel="prefetch" href="/blog/assets/js/8.f710ef8c.js"><link rel="prefetch" href="/blog/assets/js/80.cf6d2811.js"><link rel="prefetch" href="/blog/assets/js/81.6c5fdca6.js"><link rel="prefetch" href="/blog/assets/js/82.245ed394.js"><link rel="prefetch" href="/blog/assets/js/83.4b549b0f.js"><link rel="prefetch" href="/blog/assets/js/84.17cebe69.js"><link rel="prefetch" href="/blog/assets/js/85.b1179a10.js"><link rel="prefetch" href="/blog/assets/js/86.ad526400.js"><link rel="prefetch" href="/blog/assets/js/87.2eef9fa1.js"><link rel="prefetch" href="/blog/assets/js/88.92f778ed.js"><link rel="prefetch" href="/blog/assets/js/89.efe59f09.js"><link rel="prefetch" href="/blog/assets/js/9.bf9d8b8d.js"><link rel="prefetch" href="/blog/assets/js/90.26e610ca.js"><link rel="prefetch" href="/blog/assets/js/91.f78cb514.js"><link rel="prefetch" href="/blog/assets/js/92.d7983929.js"><link rel="prefetch" href="/blog/assets/js/93.20272a60.js"><link rel="prefetch" href="/blog/assets/js/94.245150bc.js"><link rel="prefetch" href="/blog/assets/js/95.6f0e48c2.js"><link rel="prefetch" href="/blog/assets/js/96.02cf7f8b.js"><link rel="prefetch" href="/blog/assets/js/97.a9438771.js"><link rel="prefetch" href="/blog/assets/js/98.12762ccb.js"><link rel="prefetch" href="/blog/assets/js/99.ddbea38c.js">
    14. 

  14.     <link rel="stylesheet" href="/blog/assets/css/0.styles.cf6c3304.css">
    15. 

  15.   </head>
    16. 

  16.   <body class="theme-mode-light">
    17. 

  17.     <div id="app" data-server-rendered="true"><div class="theme-container sidebar-open have-rightmenu"><header class="navbar blur"><div title="目录" class="sidebar-button"><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" role="img" viewBox="0 0 448 512" class="icon"><path fill="currentColor" d="M436 124H12c-6.627 0-12-5.373-12-12V80c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12z"></path></svg></div> <a href="/blog/" class="home-link router-link-active"><img src="/blog/img/logo.png" alt="彪哥博客" class="logo"> <span class="site-name can-hide">彪哥博客</span></a> <div class="links"><div class="search-box"><input aria-label="Search" autocomplete="off" spellcheck="false" value=""> <!----></div> <nav class="nav-links can-hide"><div class="nav-item"><a href="/blog/" class="nav-link">首页</a></div><div class="nav-item"><a href="http://fseller.com" target="_blank" rel="noopener noreferrer" class="nav-link external">
    18. 

  18.   个人游戏网站
    19. 

  19.   <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="前端" class="dropdown-title"><a href="/blog/web/" class="link-title">前端</a> <span class="title" style="display:none;">前端</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>前端文章</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/blog/pages/8143cc480faf9a11/" class="nav-link">JavaScript</a></li></ul></li><li class="dropdown-item"><h4>学习笔记</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/blog/note/javascript/" class="nav-link">《JavaScript教程》</a></li><li class="dropdown-subitem"><a href="/blog/note/js/" class="nav-link">《JavaScript高级程序设计》</a></li><li class="dropdown-subitem"><a href="/blog/note/es6/" class="nav-link">《ES6 教程》</a></li><li class="dropdown-subitem"><a href="/blog/note/vue/" class="nav-link">《Vue》</a></li><li class="dropdown-subitem"><a href="/blog/note/react/" class="nav-link">《React》</a></li><li class="dropdown-subitem"><a href="/blog/note/typescript-axios/" class="nav-link">《TypeScript 从零实现 axios》</a></li><li class="dropdown-subitem"><a href="/blog/note/git/" class="nav-link">《Git》</a></li><li class="dropdown-subitem"><a href="/blog/pages/51afd6/" class="nav-link">TypeScript</a></li><li class="dropdown-subitem"><a href="/blog/pages/4643cd/" class="nav-link">JS设计模式总结</a></li></ul></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="页面" class="dropdown-title"><a href="/blog/ui/" class="link-title">页面</a> <span class="title" style="display:none;">页面</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/blog/pages/8309a5b876fc95e3/" class="nav-link">HTML</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/0a83b083bdf257cb/" class="nav-link">CSS</a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="技术" class="dropdown-title"><a href="/blog/technology/" class="link-title">技术</a> <span class="title" style="display:none;">技术</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/blog/pages/9a7ee40fc232253e/" class="nav-link">技术文档</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/4c778760be26d8b3/" class="nav-link">GitHub技巧</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/117708e0af7f0bd9/" class="nav-link">Nodejs</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/41f87d890d0a02af/" class="nav-link">博客搭建</a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="更多" class="dropdown-title"><a href="/blog/more/" class="link-title">更多</a> <span class="title" style="display:none;">更多</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/blog/pages/f2a556/" class="nav-link">学习</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/aea6571b7a8bae86/" class="nav-link">面试</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/2d615df9a36a98ed/" class="nav-link">心情杂货</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/baaa02/" class="nav-link">实用技巧</a></li><li class="dropdown-item"><!----> <a href="/blog/friends/" class="nav-link">友情链接</a></li></ul></div></div><div class="nav-item"><a href="/blog/about/" class="nav-link">关于</a></div><div class="nav-item"><a href="/blog/pages/beb6c0bd8a66cea6/" class="nav-link">收藏</a></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="索引" class="dropdown-title"><a href="/blog/archives/" class="link-title">索引</a> <span class="title" style="display:none;">索引</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/blog/categories/" class="nav-link">分类</a></li><li class="dropdown-item"><!----> <a href="/blog/tags/" class="nav-link">标签</a></li><li class="dropdown-item"><!----> <a href="/blog/archives/" class="nav-link">归档</a></li></ul></div></div> <a href="https://github.com/heBody/blog" target="_blank" rel="noopener noreferrer" class="repo-link">
    20. 

  20.     GitHub
    21. 

  21.     <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav></div></header> <div class="sidebar-mask"></div> <div class="sidebar-hover-trigger"></div> <aside class="sidebar" style="display:none;"><div class="blogger"><img src="https://fastly.jsdelivr.net/gh/xugaoyi/image_store/blog/20200103123203.jpg"> <div class="blogger-info"><h3>彪哥</h3> <span>爱好前端</span></div></div> <nav class="nav-links"><div class="nav-item"><a href="/blog/" class="nav-link">首页</a></div><div class="nav-item"><a href="http://fseller.com" target="_blank" rel="noopener noreferrer" class="nav-link external">
    22. 

  22.   个人游戏网站
    23. 

  23.   <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="前端" class="dropdown-title"><a href="/blog/web/" class="link-title">前端</a> <span class="title" style="display:none;">前端</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>前端文章</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/blog/pages/8143cc480faf9a11/" class="nav-link">JavaScript</a></li></ul></li><li class="dropdown-item"><h4>学习笔记</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/blog/note/javascript/" class="nav-link">《JavaScript教程》</a></li><li class="dropdown-subitem"><a href="/blog/note/js/" class="nav-link">《JavaScript高级程序设计》</a></li><li class="dropdown-subitem"><a href="/blog/note/es6/" class="nav-link">《ES6 教程》</a></li><li class="dropdown-subitem"><a href="/blog/note/vue/" class="nav-link">《Vue》</a></li><li class="dropdown-subitem"><a href="/blog/note/react/" class="nav-link">《React》</a></li><li class="dropdown-subitem"><a href="/blog/note/typescript-axios/" class="nav-link">《TypeScript 从零实现 axios》</a></li><li class="dropdown-subitem"><a href="/blog/note/git/" class="nav-link">《Git》</a></li><li class="dropdown-subitem"><a href="/blog/pages/51afd6/" class="nav-link">TypeScript</a></li><li class="dropdown-subitem"><a href="/blog/pages/4643cd/" class="nav-link">JS设计模式总结</a></li></ul></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="页面" class="dropdown-title"><a href="/blog/ui/" class="link-title">页面</a> <span class="title" style="display:none;">页面</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/blog/pages/8309a5b876fc95e3/" class="nav-link">HTML</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/0a83b083bdf257cb/" class="nav-link">CSS</a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="技术" class="dropdown-title"><a href="/blog/technology/" class="link-title">技术</a> <span class="title" style="display:none;">技术</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/blog/pages/9a7ee40fc232253e/" class="nav-link">技术文档</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/4c778760be26d8b3/" class="nav-link">GitHub技巧</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/117708e0af7f0bd9/" class="nav-link">Nodejs</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/41f87d890d0a02af/" class="nav-link">博客搭建</a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="更多" class="dropdown-title"><a href="/blog/more/" class="link-title">更多</a> <span class="title" style="display:none;">更多</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/blog/pages/f2a556/" class="nav-link">学习</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/aea6571b7a8bae86/" class="nav-link">面试</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/2d615df9a36a98ed/" class="nav-link">心情杂货</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/baaa02/" class="nav-link">实用技巧</a></li><li class="dropdown-item"><!----> <a href="/blog/friends/" class="nav-link">友情链接</a></li></ul></div></div><div class="nav-item"><a href="/blog/about/" class="nav-link">关于</a></div><div class="nav-item"><a href="/blog/pages/beb6c0bd8a66cea6/" class="nav-link">收藏</a></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="索引" class="dropdown-title"><a href="/blog/archives/" class="link-title">索引</a> <span class="title" style="display:none;">索引</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/blog/categories/" class="nav-link">分类</a></li><li class="dropdown-item"><!----> <a href="/blog/tags/" class="nav-link">标签</a></li><li class="dropdown-item"><!----> <a href="/blog/archives/" class="nav-link">归档</a></li></ul></div></div> <a href="https://github.com/heBody/blog" target="_blank" rel="noopener noreferrer" class="repo-link">
    24. 

  24.     GitHub
    25. 

  25.     <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav>  <ul class="sidebar-links"><li><a href="/blog/pages/f344d070a1031ef7/" class="sidebar-link">ECMAScript 6 简介</a></li><li><a href="/blog/pages/c1edd70a6b7c7872/" class="sidebar-link">let 和 const 命令</a></li><li><a href="/blog/pages/b1ab10a62f7564da/" class="sidebar-link">变量的解构赋值</a></li><li><a href="/blog/pages/ca89eca8adeba5f4/" class="sidebar-link">字符串的扩展</a></li><li><a href="/blog/pages/a650b4a0ebfc9350/" class="sidebar-link">字符串的新增方法</a></li><li><a href="/blog/pages/0473261a6ab0ee8c/" class="sidebar-link">正则的扩展</a></li><li><a href="/blog/pages/5dfea9a0f2d1a392/" class="sidebar-link">数值的扩展</a></li><li><a href="/blog/pages/8ed309d668b20264/" class="sidebar-link">函数的扩展</a></li><li><a href="/blog/pages/e34009d60d8bc4b2/" class="sidebar-link">数组的扩展</a></li><li><a href="/blog/pages/b5e3e0a0ff6e9c25/" class="sidebar-link">对象的扩展</a></li><li><a href="/blog/pages/e85e68947502cf90/" class="sidebar-link">对象的新增方法</a></li><li><a href="/blog/pages/02c86eb2792f3262/" class="sidebar-link">Symbol</a></li><li><a href="/blog/pages/0c21dae358fca16b/" class="sidebar-link">Set 和 Map 数据结构</a></li><li><a href="/blog/pages/f56ec2ab97d60483/" class="sidebar-link">Proxy</a></li><li><a href="/blog/pages/74de3e45e4491e95/" class="sidebar-link">Reflect</a></li><li><a href="/blog/pages/2810ae8985e9bd52/" class="sidebar-link">Promise 对象</a></li><li><a href="/blog/pages/48df907ad3570f3d/" class="sidebar-link">Iterator 和 for-of 循环</a></li><li><a href="/blog/pages/718b48ed9ce0adce/" class="sidebar-link">Generator 函数的语法</a></li><li><a href="/blog/pages/75af7031eb66847b/" class="sidebar-link">Generator 函数的异步应用</a></li><li><a href="/blog/pages/3777253e65bac487/" class="sidebar-link">async 函数</a></li><li><a href="/blog/pages/e831e1593c82bbe0/" class="sidebar-link">Class 的基本语法</a></li><li><a href="/blog/pages/83f8c3a0cd87dd83/" class="sidebar-link">Class 的继承</a></li><li><a href="/blog/pages/efe2fb04eb8ac5fb/" class="sidebar-link">Module 的语法</a></li><li><a href="/blog/pages/a79ca2e64ceae213/" class="sidebar-link">Module 的加载实现</a></li><li><a href="/blog/pages/984bf549204bb266/" aria-current="page" class="active sidebar-link">编程风格</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level2"><a href="/blog/pages/984bf549204bb266/#块级作用域" class="sidebar-link">块级作用域</a></li><li class="sidebar-sub-header level2"><a href="/blog/pages/984bf549204bb266/#字符串" class="sidebar-link">字符串</a></li><li class="sidebar-sub-header level2"><a href="/blog/pages/984bf549204bb266/#解构赋值" class="sidebar-link">解构赋值</a></li><li class="sidebar-sub-header level2"><a href="/blog/pages/984bf549204bb266/#对象" class="sidebar-link">对象</a></li><li class="sidebar-sub-header level2"><a href="/blog/pages/984bf549204bb266/#数组" class="sidebar-link">数组</a></li><li class="sidebar-sub-header level2"><a href="/blog/pages/984bf549204bb266/#函数" class="sidebar-link">函数</a></li><li class="sidebar-sub-header level2"><a href="/blog/pages/984bf549204bb266/#map-结构" class="sidebar-link">Map 结构</a></li><li class="sidebar-sub-header level2"><a href="/blog/pages/984bf549204bb266/#class" class="sidebar-link">Class</a></li><li class="sidebar-sub-header level2"><a href="/blog/pages/984bf549204bb266/#模块" class="sidebar-link">模块</a></li><li class="sidebar-sub-header level2"><a href="/blog/pages/984bf549204bb266/#eslint-的使用" class="sidebar-link">ESLint 的使用</a></li></ul></li><li><a href="/blog/pages/32c35f7651d6e58e/" class="sidebar-link">读懂 ECMAScript 规格</a></li><li><a href="/blog/pages/16121351be68691b/" class="sidebar-link">异步遍历器</a></li><li><a href="/blog/pages/a2ba314746bfdbdd/" class="sidebar-link">ArrayBuffer</a></li><li><a href="/blog/pages/7188882b8d65af1b/" class="sidebar-link">最新提案</a></li><li><a href="/blog/pages/e97bc1e5626b082c/" class="sidebar-link">装饰器</a></li><li><a href="/blog/pages/1cf50330655efc69/" class="sidebar-link">函数式编程</a></li><li><a href="/blog/pages/6a8e2dc558da1b39/" class="sidebar-link">Mixin</a></li><li><a href="/blog/pages/8e8f80f69b775a56/" class="sidebar-link">SIMD</a></li><li><a href="/blog/pages/ea6f3b870f6dab69/" class="sidebar-link">参考链接</a></li></ul> </aside> <div><main class="page"><div class="theme-vdoing-wrapper "><div class="articleInfo-wrap" data-v-06225672><div class="articleInfo" data-v-06225672><ul class="breadcrumbs" data-v-06225672><li data-v-06225672><a href="/blog/" title="首页" class="iconfont icon-home router-link-active" data-v-06225672></a></li> <li data-v-06225672><a href="/blog/note/es6/#《ES6 教程》笔记" data-v-06225672>《ES6 教程》笔记</a></li></ul> <div class="info" data-v-06225672><div title="作者" class="author iconfont icon-touxiang" data-v-06225672><a href="javascript:;" data-v-06225672>阮一峰</a></div> <div title="创建时间" class="date iconfont icon-riqi" data-v-06225672><a href="javascript:;" data-v-06225672>2020-02-09</a></div> <!----></div></div></div> <!----> <div class="content-wrapper"><div class="right-menu-wrapper"><div class="right-menu-margin"><div class="right-menu-title">目录</div> <div class="right-menu-content"></div></div></div> <h1><img src="data:image/png;base64,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">编程风格<!----></h1>  <div class="theme-vdoing-content content__default"><h1 id="编程风格"><a href="#编程风格" class="header-anchor">#</a> 编程风格</h1> <p>本章探讨如何将 ES6 的新语法，运用到编码实践之中，与传统的 JavaScript 语法结合在一起，写出合理的、易于阅读和维护的代码。</p> <p>多家公司和组织已经公开了它们的风格规范，下面的内容主要参考了 <a href="https://github.com/airbnb/javascript" target="_blank" rel="noopener noreferrer">Airbnb<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a> 公司的 JavaScript 风格规范。
    26. 

  26. </p> <h2 id="块级作用域"><a href="#块级作用域" class="header-anchor">#</a> 块级作用域</h2> <p><strong>（1）let 取代 var</strong></p> <p>ES6 提出了两个新的声明变量的命令：<code>let</code>和<code>const</code>。其中，<code>let</code>完全可以取代<code>var</code>，因为两者语义相同，而且<code>let</code>没有副作用。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token string">'use strict'</span><span class="token punctuation">;</span>
    27. 

  27. 

  28. <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token boolean">true</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    29. 

  29.   <span class="token keyword">let</span> x <span class="token operator">=</span> <span class="token string">'hello'</span><span class="token punctuation">;</span>
    30. 

  30. <span class="token punctuation">}</span>
    31. 

  31. 

  32. <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">let</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> <span class="token number">10</span><span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    33. 

  33.   console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>i<span class="token punctuation">)</span><span class="token punctuation">;</span>
    34. 

  34. <span class="token punctuation">}</span>
    35. 

  35. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br></div></div><p>上面代码如果用<code>var</code>替代<code>let</code>，实际上就声明了两个全局变量，这显然不是本意。变量应该只在其声明的代码块内有效，<code>var</code>命令做不到这一点。</p> <p><code>var</code>命令存在变量提升效用，<code>let</code>命令没有这个问题。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token string">'use strict'</span><span class="token punctuation">;</span>
    36. 

  36. 

  37. <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token boolean">true</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    38. 

  38.   console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>x<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// ReferenceError</span>
    39. 

  39.   <span class="token keyword">let</span> x <span class="token operator">=</span> <span class="token string">'hello'</span><span class="token punctuation">;</span>
    40. 

  40. <span class="token punctuation">}</span>
    41. 

  41. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br></div></div><p>上面代码如果使用<code>var</code>替代<code>let</code>，<code>console.log</code>那一行就不会报错，而是会输出<code>undefined</code>，因为变量声明提升到代码块的头部。这违反了变量先声明后使用的原则。</p> <p>所以，建议不再使用<code>var</code>命令，而是使用<code>let</code>命令取代。</p> <p><strong>（2）全局常量和线程安全</strong></p> <p>在<code>let</code>和<code>const</code>之间，建议优先使用<code>const</code>，尤其是在全局环境，不应该设置变量，只应设置常量。</p> <p><code>const</code>优于<code>let</code>有几个原因。一个是<code>const</code>可以提醒阅读程序的人，这个变量不应该改变；另一个是<code>const</code>比较符合函数式编程思想，运算不改变值，只是新建值，而且这样也有利于将来的分布式运算；最后一个原因是 JavaScript <strong>编译器会对<code>const</code>进行优化</strong>，所以多使用<code>const</code>，有利于提高程序的运行效率，也就是说<code>let</code>和<code>const</code>的本质区别，其实是编译器内部的处理不同。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    42. 

  42. <span class="token keyword">var</span> a <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">,</span> b <span class="token operator">=</span> <span class="token number">2</span><span class="token punctuation">,</span> c <span class="token operator">=</span> <span class="token number">3</span><span class="token punctuation">;</span>
    43. 

  43. 

  44. <span class="token comment">// good</span>
    45. 

  45. <span class="token keyword">const</span> a <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span>
    46. 

  46. <span class="token keyword">const</span> b <span class="token operator">=</span> <span class="token number">2</span><span class="token punctuation">;</span>
    47. 

  47. <span class="token keyword">const</span> c <span class="token operator">=</span> <span class="token number">3</span><span class="token punctuation">;</span>
    48. 

  48. 

  49. <span class="token comment">// best</span>
    50. 

  50. <span class="token keyword">const</span> <span class="token punctuation">[</span>a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> c<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
    51. 

  51. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br></div></div><p><code>const</code>声明常量还有两个好处，一是阅读代码的人立刻会意识到不应该修改这个值，二是防止了无意间修改变量值所导致的错误。</p> <p>所有的函数都应该设置为常量。</p> <p>长远来看，JavaScript 可能会有多线程的实现（比如 Intel 公司的 River Trail 那一类的项目），这时<code>let</code>表示的变量，只应出现在单线程运行的代码中，不能是多线程共享的，这样有利于保证线程安全。</p> <h2 id="字符串"><a href="#字符串" class="header-anchor">#</a> 字符串</h2> <p>静态字符串一律使用单引号或反引号，不使用双引号。动态字符串使用反引号。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    52. 

  52. <span class="token keyword">const</span> a <span class="token operator">=</span> <span class="token string">&quot;foobar&quot;</span><span class="token punctuation">;</span>
    53. 

  53. <span class="token keyword">const</span> b <span class="token operator">=</span> <span class="token string">'foo'</span> <span class="token operator">+</span> a <span class="token operator">+</span> <span class="token string">'bar'</span><span class="token punctuation">;</span>
    54. 

  54. 

  55. <span class="token comment">// acceptable</span>
    56. 

  56. <span class="token keyword">const</span> c <span class="token operator">=</span> <span class="token template-string"><span class="token template-punctuation string">`</span><span class="token string">foobar</span><span class="token template-punctuation string">`</span></span><span class="token punctuation">;</span>
    57. 

  57. 

  58. <span class="token comment">// good</span>
    59. 

  59. <span class="token keyword">const</span> a <span class="token operator">=</span> <span class="token string">'foobar'</span><span class="token punctuation">;</span>
    60. 

  60. <span class="token keyword">const</span> b <span class="token operator">=</span> <span class="token template-string"><span class="token template-punctuation string">`</span><span class="token string">foo</span><span class="token interpolation"><span class="token interpolation-punctuation punctuation">${</span>a<span class="token interpolation-punctuation punctuation">}</span></span><span class="token string">bar</span><span class="token template-punctuation string">`</span></span><span class="token punctuation">;</span>
    61. 

  61. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br></div></div><h2 id="解构赋值"><a href="#解构赋值" class="header-anchor">#</a> 解构赋值</h2> <p>使用数组成员对变量赋值时，优先使用解构赋值。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">const</span> arr <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
    62. 

  62. 

  63. <span class="token comment">// bad</span>
    64. 

  64. <span class="token keyword">const</span> first <span class="token operator">=</span> arr<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
    65. 

  65. <span class="token keyword">const</span> second <span class="token operator">=</span> arr<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
    66. 

  66. 

  67. <span class="token comment">// good</span>
    68. 

  68. <span class="token keyword">const</span> <span class="token punctuation">[</span>first<span class="token punctuation">,</span> second<span class="token punctuation">]</span> <span class="token operator">=</span> arr<span class="token punctuation">;</span>
    69. 

  69. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br></div></div><p>函数的参数如果是对象的成员，优先使用解构赋值。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    70. 

  70. <span class="token keyword">function</span> <span class="token function">getFullName</span><span class="token punctuation">(</span><span class="token parameter">user</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    71. 

  71.   <span class="token keyword">const</span> firstName <span class="token operator">=</span> user<span class="token punctuation">.</span>firstName<span class="token punctuation">;</span>
    72. 

  72.   <span class="token keyword">const</span> lastName <span class="token operator">=</span> user<span class="token punctuation">.</span>lastName<span class="token punctuation">;</span>
    73. 

  73. <span class="token punctuation">}</span>
    74. 

  74. 

  75. <span class="token comment">// good</span>
    76. 

  76. <span class="token keyword">function</span> <span class="token function">getFullName</span><span class="token punctuation">(</span><span class="token parameter">obj</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    77. 

  77.   <span class="token keyword">const</span> <span class="token punctuation">{</span> firstName<span class="token punctuation">,</span> lastName <span class="token punctuation">}</span> <span class="token operator">=</span> obj<span class="token punctuation">;</span>
    78. 

  78. <span class="token punctuation">}</span>
    79. 

  79. 

  80. <span class="token comment">// best</span>
    81. 

  81. <span class="token keyword">function</span> <span class="token function">getFullName</span><span class="token punctuation">(</span><span class="token parameter"><span class="token punctuation">{</span> firstName<span class="token punctuation">,</span> lastName <span class="token punctuation">}</span></span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    82. 

  82. <span class="token punctuation">}</span>
    83. 

  83. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br></div></div><p>如果函数返回多个值，优先使用对象的解构赋值，而不是数组的解构赋值。这样便于以后添加返回值，以及更改返回值的顺序。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    84. 

  84. <span class="token keyword">function</span> <span class="token function">processInput</span><span class="token punctuation">(</span><span class="token parameter">input</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    85. 

  85.   <span class="token keyword">return</span> <span class="token punctuation">[</span>left<span class="token punctuation">,</span> right<span class="token punctuation">,</span> top<span class="token punctuation">,</span> bottom<span class="token punctuation">]</span><span class="token punctuation">;</span>
    86. 

  86. <span class="token punctuation">}</span>
    87. 

  87. 

  88. <span class="token comment">// good</span>
    89. 

  89. <span class="token keyword">function</span> <span class="token function">processInput</span><span class="token punctuation">(</span><span class="token parameter">input</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    90. 

  90.   <span class="token keyword">return</span> <span class="token punctuation">{</span> left<span class="token punctuation">,</span> right<span class="token punctuation">,</span> top<span class="token punctuation">,</span> bottom <span class="token punctuation">}</span><span class="token punctuation">;</span>
    91. 

  91. <span class="token punctuation">}</span>
    92. 

  92. 

  93. <span class="token keyword">const</span> <span class="token punctuation">{</span> left<span class="token punctuation">,</span> right <span class="token punctuation">}</span> <span class="token operator">=</span> <span class="token function">processInput</span><span class="token punctuation">(</span>input<span class="token punctuation">)</span><span class="token punctuation">;</span>
    94. 

  94. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br></div></div><h2 id="对象"><a href="#对象" class="header-anchor">#</a> 对象</h2> <p>单行定义的对象，最后一个成员不以逗号结尾。多行定义的对象，<strong>最后一个成员以逗号结尾</strong>。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    95. 

  95. <span class="token keyword">const</span> a <span class="token operator">=</span> <span class="token punctuation">{</span> <span class="token literal-property property">k1</span><span class="token operator">:</span> v1<span class="token punctuation">,</span> <span class="token literal-property property">k2</span><span class="token operator">:</span> v2<span class="token punctuation">,</span> <span class="token punctuation">}</span><span class="token punctuation">;</span>
    96. 

  96. <span class="token keyword">const</span> b <span class="token operator">=</span> <span class="token punctuation">{</span>
    97. 

  97.   <span class="token literal-property property">k1</span><span class="token operator">:</span> v1<span class="token punctuation">,</span>
    98. 

  98.   <span class="token literal-property property">k2</span><span class="token operator">:</span> v2
    99. 

  99. <span class="token punctuation">}</span><span class="token punctuation">;</span>
    100. 

  100. 

  101. <span class="token comment">// good</span>
    102. 

  102. <span class="token keyword">const</span> a <span class="token operator">=</span> <span class="token punctuation">{</span> <span class="token literal-property property">k1</span><span class="token operator">:</span> v1<span class="token punctuation">,</span> <span class="token literal-property property">k2</span><span class="token operator">:</span> v2 <span class="token punctuation">}</span><span class="token punctuation">;</span>
    103. 

  103. <span class="token keyword">const</span> b <span class="token operator">=</span> <span class="token punctuation">{</span>
    104. 

  104.   <span class="token literal-property property">k1</span><span class="token operator">:</span> v1<span class="token punctuation">,</span>
    105. 

  105.   <span class="token literal-property property">k2</span><span class="token operator">:</span> v2<span class="token punctuation">,</span>
    106. 

  106. <span class="token punctuation">}</span><span class="token punctuation">;</span>
    107. 

  107. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br></div></div><p>对象尽量静态化，一旦定义，就不得随意添加新的属性。如果添加属性不可避免，要使用<code>Object.assign</code>方法。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    108. 

  108. <span class="token keyword">const</span> a <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
    109. 

  109. a<span class="token punctuation">.</span>x <span class="token operator">=</span> <span class="token number">3</span><span class="token punctuation">;</span>
    110. 

  110. 

  111. <span class="token comment">// if reshape unavoidable</span>
    112. 

  112. <span class="token keyword">const</span> a <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
    113. 

  113. Object<span class="token punctuation">.</span><span class="token function">assign</span><span class="token punctuation">(</span>a<span class="token punctuation">,</span> <span class="token punctuation">{</span> <span class="token literal-property property">x</span><span class="token operator">:</span> <span class="token number">3</span> <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    114. 

  114. 

  115. <span class="token comment">// good</span>
    116. 

  116. <span class="token keyword">const</span> a <span class="token operator">=</span> <span class="token punctuation">{</span> <span class="token literal-property property">x</span><span class="token operator">:</span> <span class="token keyword">null</span> <span class="token punctuation">}</span><span class="token punctuation">;</span>
    117. 

  117. a<span class="token punctuation">.</span>x <span class="token operator">=</span> <span class="token number">3</span><span class="token punctuation">;</span>
    118. 

  118. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br></div></div><p>如果对象的属性名是动态的，可以在创造对象的时候，使用属性表达式定义。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    119. 

  119. <span class="token keyword">const</span> obj <span class="token operator">=</span> <span class="token punctuation">{</span>
    120. 

  120.   <span class="token literal-property property">id</span><span class="token operator">:</span> <span class="token number">5</span><span class="token punctuation">,</span>
    121. 

  121.   <span class="token literal-property property">name</span><span class="token operator">:</span> <span class="token string">'San Francisco'</span><span class="token punctuation">,</span>
    122. 

  122. <span class="token punctuation">}</span><span class="token punctuation">;</span>
    123. 

  123. obj<span class="token punctuation">[</span><span class="token function">getKey</span><span class="token punctuation">(</span><span class="token string">'enabled'</span><span class="token punctuation">)</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
    124. 

  124. 

  125. <span class="token comment">// good</span>
    126. 

  126. <span class="token keyword">const</span> obj <span class="token operator">=</span> <span class="token punctuation">{</span>
    127. 

  127.   <span class="token literal-property property">id</span><span class="token operator">:</span> <span class="token number">5</span><span class="token punctuation">,</span>
    128. 

  128.   <span class="token literal-property property">name</span><span class="token operator">:</span> <span class="token string">'San Francisco'</span><span class="token punctuation">,</span>
    129. 

  129.   <span class="token punctuation">[</span><span class="token function">getKey</span><span class="token punctuation">(</span><span class="token string">'enabled'</span><span class="token punctuation">)</span><span class="token punctuation">]</span><span class="token operator">:</span> <span class="token boolean">true</span><span class="token punctuation">,</span>
    130. 

  130. <span class="token punctuation">}</span><span class="token punctuation">;</span>
    131. 

  131. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br></div></div><p>上面代码中，对象<code>obj</code>的最后一个属性名，需要计算得到。这时最好采用属性表达式，在新建<code>obj</code>的时候，将该属性与其他属性定义在一起。这样一来，所有属性就在一个地方定义了。</p> <p>另外，对象的属性和方法，<strong>尽量采用简洁表达法</strong>，这样易于描述和书写。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">var</span> ref <span class="token operator">=</span> <span class="token string">'some value'</span><span class="token punctuation">;</span>
    132. 

  132. 

  133. <span class="token comment">// bad</span>
    134. 

  134. <span class="token keyword">const</span> atom <span class="token operator">=</span> <span class="token punctuation">{</span>
    135. 

  135.   <span class="token literal-property property">ref</span><span class="token operator">:</span> ref<span class="token punctuation">,</span>
    136. 

  136. 

  137.   <span class="token literal-property property">value</span><span class="token operator">:</span> <span class="token number">1</span><span class="token punctuation">,</span>
    138. 

  138. 

  139.   <span class="token function-variable function">addValue</span><span class="token operator">:</span> <span class="token keyword">function</span> <span class="token punctuation">(</span><span class="token parameter">value</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    140. 

  140.     <span class="token keyword">return</span> atom<span class="token punctuation">.</span>value <span class="token operator">+</span> value<span class="token punctuation">;</span>
    141. 

  141.   <span class="token punctuation">}</span><span class="token punctuation">,</span>
    142. 

  142. <span class="token punctuation">}</span><span class="token punctuation">;</span>
    143. 

  143. 

  144. <span class="token comment">// good</span>
    145. 

  145. <span class="token keyword">const</span> atom <span class="token operator">=</span> <span class="token punctuation">{</span>
    146. 

  146.   ref<span class="token punctuation">,</span>
    147. 

  147. 

  148.   <span class="token literal-property property">value</span><span class="token operator">:</span> <span class="token number">1</span><span class="token punctuation">,</span>
    149. 

  149. 

  150.   <span class="token function">addValue</span><span class="token punctuation">(</span><span class="token parameter">value</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    151. 

  151.     <span class="token keyword">return</span> atom<span class="token punctuation">.</span>value <span class="token operator">+</span> value<span class="token punctuation">;</span>
    152. 

  152.   <span class="token punctuation">}</span><span class="token punctuation">,</span>
    153. 

  153. <span class="token punctuation">}</span><span class="token punctuation">;</span>
    154. 

  154. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br></div></div><h2 id="数组"><a href="#数组" class="header-anchor">#</a> 数组</h2> <p>使用<strong>扩展运算符（...）拷贝数组</strong>。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    155. 

  155. <span class="token keyword">const</span> len <span class="token operator">=</span> items<span class="token punctuation">.</span>length<span class="token punctuation">;</span>
    156. 

  156. <span class="token keyword">const</span> itemsCopy <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
    157. 

  157. <span class="token keyword">let</span> i<span class="token punctuation">;</span>
    158. 

  158. 

  159. <span class="token keyword">for</span> <span class="token punctuation">(</span>i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> len<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    160. 

  160.   itemsCopy<span class="token punctuation">[</span>i<span class="token punctuation">]</span> <span class="token operator">=</span> items<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">;</span>
    161. 

  161. <span class="token punctuation">}</span>
    162. 

  162. 

  163. <span class="token comment">// good</span>
    164. 

  164. <span class="token keyword">const</span> itemsCopy <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token operator">...</span>items<span class="token punctuation">]</span><span class="token punctuation">;</span>
    165. 

  165. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br></div></div><p>使用 <strong>Array.from 方法，将类似数组的对象转为数组</strong>。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">const</span> foo <span class="token operator">=</span> document<span class="token punctuation">.</span><span class="token function">querySelectorAll</span><span class="token punctuation">(</span><span class="token string">'.foo'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    166. 

  166. <span class="token keyword">const</span> nodes <span class="token operator">=</span> Array<span class="token punctuation">.</span><span class="token function">from</span><span class="token punctuation">(</span>foo<span class="token punctuation">)</span><span class="token punctuation">;</span>
    167. 

  167. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><h2 id="函数"><a href="#函数" class="header-anchor">#</a> 函数</h2> <p>立即执行函数可以写成箭头函数的形式。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
    168. 

  168.   console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">'Welcome to the Internet.'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    169. 

  169. <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    170. 

  170. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><p>那些使用匿名函数当作参数的场合，<strong>尽量用箭头函数代替</strong>。因为这样更简洁，而且绑定了 this。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    171. 

  171. <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">.</span><span class="token function">map</span><span class="token punctuation">(</span><span class="token keyword">function</span> <span class="token punctuation">(</span><span class="token parameter">x</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    172. 

  172.   <span class="token keyword">return</span> x <span class="token operator">*</span> x<span class="token punctuation">;</span>
    173. 

  173. <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    174. 

  174. 

  175. <span class="token comment">// good</span>
    176. 

  176. <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">.</span><span class="token function">map</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token parameter">x</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
    177. 

  177.   <span class="token keyword">return</span> x <span class="token operator">*</span> x<span class="token punctuation">;</span>
    178. 

  178. <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    179. 

  179. 

  180. <span class="token comment">// best</span>
    181. 

  181. <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">.</span><span class="token function">map</span><span class="token punctuation">(</span><span class="token parameter">x</span> <span class="token operator">=&gt;</span> x <span class="token operator">*</span> x<span class="token punctuation">)</span><span class="token punctuation">;</span>
    182. 

  182. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br></div></div><p>箭头函数取代<code>Function.prototype.bind</code>，不应再用 self/_this/that 绑定 this。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    183. 

  183. <span class="token keyword">const</span> self <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">;</span>
    184. 

  184. <span class="token keyword">const</span> <span class="token function-variable function">boundMethod</span> <span class="token operator">=</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token parameter"><span class="token operator">...</span>params</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    185. 

  185.   <span class="token keyword">return</span> <span class="token function">method</span><span class="token punctuation">.</span><span class="token function">apply</span><span class="token punctuation">(</span>self<span class="token punctuation">,</span> params<span class="token punctuation">)</span><span class="token punctuation">;</span>
    186. 

  186. <span class="token punctuation">}</span>
    187. 

  187. 

  188. <span class="token comment">// acceptable</span>
    189. 

  189. <span class="token keyword">const</span> boundMethod <span class="token operator">=</span> <span class="token function">method</span><span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    190. 

  190. 

  191. <span class="token comment">// best</span>
    192. 

  192. <span class="token keyword">const</span> <span class="token function-variable function">boundMethod</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token parameter"><span class="token operator">...</span>params</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token function">method</span><span class="token punctuation">.</span><span class="token function">apply</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">,</span> params<span class="token punctuation">)</span><span class="token punctuation">;</span>
    193. 

  193. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br></div></div><p>简单的、单行的、不会复用的函数，建议采用箭头函数。<strong>如果函数体较为复杂，行数较多，还是应该采用传统的函数写法。</strong></p> <p><strong>所有配置项都应该集中在一个对象，放在最后一个参数，布尔值不可以直接作为参数</strong>。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    194. 

  194. <span class="token keyword">function</span> <span class="token function">divide</span><span class="token punctuation">(</span><span class="token parameter">a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> option <span class="token operator">=</span> <span class="token boolean">false</span></span> <span class="token punctuation">)</span> <span class="token punctuation">{</span>
    195. 

  195. <span class="token punctuation">}</span>
    196. 

  196. 

  197. <span class="token comment">// good</span>
    198. 

  198. <span class="token keyword">function</span> <span class="token function">divide</span><span class="token punctuation">(</span><span class="token parameter">a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> <span class="token punctuation">{</span> option <span class="token operator">=</span> <span class="token boolean">false</span> <span class="token punctuation">}</span> <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span></span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    199. 

  199. <span class="token punctuation">}</span>
    200. 

  200. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br></div></div><p>不要在函数体内使用 arguments 变量，使用 rest 运算符（...）代替。因为 rest 运算符显式表明你想要获取参数，而且 arguments 是一个类似数组的对象，而 rest 运算符可以提供一个真正的数组。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    201. 

  201. <span class="token keyword">function</span> <span class="token function">concatenateAll</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    202. 

  202.   <span class="token keyword">const</span> args <span class="token operator">=</span> <span class="token class-name">Array</span><span class="token punctuation">.</span>prototype<span class="token punctuation">.</span><span class="token function">slice</span><span class="token punctuation">.</span><span class="token function">call</span><span class="token punctuation">(</span>arguments<span class="token punctuation">)</span><span class="token punctuation">;</span>
    203. 

  203.   <span class="token keyword">return</span> args<span class="token punctuation">.</span><span class="token function">join</span><span class="token punctuation">(</span><span class="token string">''</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    204. 

  204. <span class="token punctuation">}</span>
    205. 

  205. 

  206. <span class="token comment">// good</span>
    207. 

  207. <span class="token keyword">function</span> <span class="token function">concatenateAll</span><span class="token punctuation">(</span><span class="token parameter"><span class="token operator">...</span>args</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    208. 

  208.   <span class="token keyword">return</span> args<span class="token punctuation">.</span><span class="token function">join</span><span class="token punctuation">(</span><span class="token string">''</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    209. 

  209. <span class="token punctuation">}</span>
    210. 

  210. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br></div></div><p>使用默认值语法设置函数参数的默认值。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    211. 

  211. <span class="token keyword">function</span> <span class="token function">handleThings</span><span class="token punctuation">(</span><span class="token parameter">opts</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    212. 

  212.   opts <span class="token operator">=</span> opts <span class="token operator">||</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
    213. 

  213. <span class="token punctuation">}</span>
    214. 

  214. 

  215. <span class="token comment">// good</span>
    216. 

  216. <span class="token keyword">function</span> <span class="token function">handleThings</span><span class="token punctuation">(</span><span class="token parameter">opts <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span></span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    217. 

  217.   <span class="token comment">// ...</span>
    218. 

  218. <span class="token punctuation">}</span>
    219. 

  219. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br></div></div><h2 id="map-结构"><a href="#map-结构" class="header-anchor">#</a> Map 结构</h2> <p>注意区分 Object 和 Map，只有模拟现实世界的实体对象时，才使用 Object。如果只是需要<code>key: value</code>的数据结构，使用 Map 结构。因为 Map 有内建的遍历机制。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">let</span> map <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Map</span><span class="token punctuation">(</span>arr<span class="token punctuation">)</span><span class="token punctuation">;</span>
    220. 

  220. 

  221. <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">let</span> key <span class="token keyword">of</span> map<span class="token punctuation">.</span><span class="token function">keys</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    222. 

  222.   console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>key<span class="token punctuation">)</span><span class="token punctuation">;</span>
    223. 

  223. <span class="token punctuation">}</span>
    224. 

  224. 

  225. <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">let</span> value <span class="token keyword">of</span> map<span class="token punctuation">.</span><span class="token function">values</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    226. 

  226.   console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>value<span class="token punctuation">)</span><span class="token punctuation">;</span>
    227. 

  227. <span class="token punctuation">}</span>
    228. 

  228. 

  229. <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">let</span> item <span class="token keyword">of</span> map<span class="token punctuation">.</span><span class="token function">entries</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    230. 

  230.   console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>item<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">,</span> item<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    231. 

  231. <span class="token punctuation">}</span>
    232. 

  232. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br></div></div><h2 id="class"><a href="#class" class="header-anchor">#</a> Class</h2> <p>总是用 Class，取代需要 prototype 的操作。因为 Class 的写法更简洁，更易于理解。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    233. 

  233. <span class="token keyword">function</span> <span class="token function">Queue</span><span class="token punctuation">(</span><span class="token parameter">contents <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">]</span></span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    234. 

  234.   <span class="token keyword">this</span><span class="token punctuation">.</span>_queue <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token operator">...</span>contents<span class="token punctuation">]</span><span class="token punctuation">;</span>
    235. 

  235. <span class="token punctuation">}</span>
    236. 

  236. <span class="token class-name">Queue</span><span class="token punctuation">.</span>prototype<span class="token punctuation">.</span><span class="token function-variable function">pop</span> <span class="token operator">=</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    237. 

  237.   <span class="token keyword">const</span> value <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>_queue<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
    238. 

  238.   <span class="token keyword">this</span><span class="token punctuation">.</span>_queue<span class="token punctuation">.</span><span class="token function">splice</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    239. 

  239.   <span class="token keyword">return</span> value<span class="token punctuation">;</span>
    240. 

  240. <span class="token punctuation">}</span>
    241. 

  241. 

  242. <span class="token comment">// good</span>
    243. 

  243. <span class="token keyword">class</span> <span class="token class-name">Queue</span> <span class="token punctuation">{</span>
    244. 

  244.   <span class="token function">constructor</span><span class="token punctuation">(</span><span class="token parameter">contents <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">]</span></span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    245. 

  245.     <span class="token keyword">this</span><span class="token punctuation">.</span>_queue <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token operator">...</span>contents<span class="token punctuation">]</span><span class="token punctuation">;</span>
    246. 

  246.   <span class="token punctuation">}</span>
    247. 

  247.   <span class="token function">pop</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    248. 

  248.     <span class="token keyword">const</span> value <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>_queue<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
    249. 

  249.     <span class="token keyword">this</span><span class="token punctuation">.</span>_queue<span class="token punctuation">.</span><span class="token function">splice</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    250. 

  250.     <span class="token keyword">return</span> value<span class="token punctuation">;</span>
    251. 

  251.   <span class="token punctuation">}</span>
    252. 

  252. <span class="token punctuation">}</span>
    253. 

  253. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br></div></div><p>使用<code>extends</code>实现继承，因为这样更简单，不会有破坏<code>instanceof</code>运算的危险。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    254. 

  254. <span class="token keyword">const</span> inherits <span class="token operator">=</span> <span class="token function">require</span><span class="token punctuation">(</span><span class="token string">'inherits'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    255. 

  255. <span class="token keyword">function</span> <span class="token function">PeekableQueue</span><span class="token punctuation">(</span><span class="token parameter">contents</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    256. 

  256.   <span class="token function">Queue</span><span class="token punctuation">.</span><span class="token function">apply</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">,</span> contents<span class="token punctuation">)</span><span class="token punctuation">;</span>
    257. 

  257. <span class="token punctuation">}</span>
    258. 

  258. <span class="token function">inherits</span><span class="token punctuation">(</span>PeekableQueue<span class="token punctuation">,</span> Queue<span class="token punctuation">)</span><span class="token punctuation">;</span>
    259. 

  259. <span class="token class-name">PeekableQueue</span><span class="token punctuation">.</span>prototype<span class="token punctuation">.</span><span class="token function-variable function">peek</span> <span class="token operator">=</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    260. 

  260.   <span class="token keyword">return</span> <span class="token keyword">this</span><span class="token punctuation">.</span>_queue<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
    261. 

  261. <span class="token punctuation">}</span>
    262. 

  262. 

  263. <span class="token comment">// good</span>
    264. 

  264. <span class="token keyword">class</span> <span class="token class-name">PeekableQueue</span> <span class="token keyword">extends</span> <span class="token class-name">Queue</span> <span class="token punctuation">{</span>
    265. 

  265.   <span class="token function">peek</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    266. 

  266.     <span class="token keyword">return</span> <span class="token keyword">this</span><span class="token punctuation">.</span>_queue<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
    267. 

  267.   <span class="token punctuation">}</span>
    268. 

  268. <span class="token punctuation">}</span>
    269. 

  269. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br></div></div><h2 id="模块"><a href="#模块" class="header-anchor">#</a> 模块</h2> <p>首先，Module 语法是 JavaScript 模块的标准写法，坚持使用这种写法。使用<code>import</code>取代<code>require</code>。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    270. 

  270. <span class="token keyword">const</span> moduleA <span class="token operator">=</span> <span class="token function">require</span><span class="token punctuation">(</span><span class="token string">'moduleA'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    271. 

  271. <span class="token keyword">const</span> func1 <span class="token operator">=</span> moduleA<span class="token punctuation">.</span>func1<span class="token punctuation">;</span>
    272. 

  272. <span class="token keyword">const</span> func2 <span class="token operator">=</span> moduleA<span class="token punctuation">.</span>func2<span class="token punctuation">;</span>
    273. 

  273. 

  274. <span class="token comment">// good</span>
    275. 

  275. <span class="token keyword">import</span> <span class="token punctuation">{</span> func1<span class="token punctuation">,</span> func2 <span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'moduleA'</span><span class="token punctuation">;</span>
    276. 

  276. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br></div></div><p>使用<code>export</code>取代<code>module.exports</code>。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// commonJS的写法</span>
    277. 

  277. <span class="token keyword">var</span> React <span class="token operator">=</span> <span class="token function">require</span><span class="token punctuation">(</span><span class="token string">'react'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    278. 

  278. 

  279. <span class="token keyword">var</span> Breadcrumbs <span class="token operator">=</span> React<span class="token punctuation">.</span><span class="token function">createClass</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
    280. 

  280.   <span class="token function">render</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    281. 

  281.     <span class="token keyword">return</span> <span class="token operator">&lt;</span>nav <span class="token operator">/</span><span class="token operator">&gt;</span><span class="token punctuation">;</span>
    282. 

  282.   <span class="token punctuation">}</span>
    283. 

  283. <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    284. 

  284. 

  285. module<span class="token punctuation">.</span>exports <span class="token operator">=</span> Breadcrumbs<span class="token punctuation">;</span>
    286. 

  286. 

  287. <span class="token comment">// ES6的写法</span>
    288. 

  288. <span class="token keyword">import</span> React <span class="token keyword">from</span> <span class="token string">'react'</span><span class="token punctuation">;</span>
    289. 

  289. 

  290. <span class="token keyword">class</span> <span class="token class-name">Breadcrumbs</span> <span class="token keyword">extends</span> <span class="token class-name">React<span class="token punctuation">.</span>Component</span> <span class="token punctuation">{</span>
    291. 

  291.   <span class="token function">render</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    292. 

  292.     <span class="token keyword">return</span> <span class="token operator">&lt;</span>nav <span class="token operator">/</span><span class="token operator">&gt;</span><span class="token punctuation">;</span>
    293. 

  293.   <span class="token punctuation">}</span>
    294. 

  294. <span class="token punctuation">}</span><span class="token punctuation">;</span>
    295. 

  295. 

  296. <span class="token keyword">export</span> <span class="token keyword">default</span> Breadcrumbs<span class="token punctuation">;</span>
    297. 

  297. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br></div></div><p>如果模块只有一个输出值，就使用<code>export default</code>，如果模块有多个输出值，就不使用<code>export default</code>，<code>export default</code>与普通的<code>export</code>不要同时使用。</p> <p>不要在模块输入中使用通配符。因为这样可以确保你的模块之中，有一个默认输出（export default）。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token comment">// bad</span>
    298. 

  298. <span class="token keyword">import</span> <span class="token operator">*</span> <span class="token keyword">as</span> myObject <span class="token keyword">from</span> <span class="token string">'./importModule'</span><span class="token punctuation">;</span>
    299. 

  299. 

  300. <span class="token comment">// good</span>
    301. 

  301. <span class="token keyword">import</span> myObject <span class="token keyword">from</span> <span class="token string">'./importModule'</span><span class="token punctuation">;</span>
    302. 

  302. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><p>如果模块默认输出一个函数，函数名的首字母应该小写。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">function</span> <span class="token function">makeStyleGuide</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    303. 

  303. <span class="token punctuation">}</span>
    304. 

  304. 

  305. <span class="token keyword">export</span> <span class="token keyword">default</span> makeStyleGuide<span class="token punctuation">;</span>
    306. 

  306. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><p>如果模块默认输出一个对象，对象名的首字母应该大写。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">const</span> StyleGuide <span class="token operator">=</span> <span class="token punctuation">{</span>
    307. 

  307.   <span class="token literal-property property">es6</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    308. 

  308.   <span class="token punctuation">}</span>
    309. 

  309. <span class="token punctuation">}</span><span class="token punctuation">;</span>
    310. 

  310. 

  311. <span class="token keyword">export</span> <span class="token keyword">default</span> StyleGuide<span class="token punctuation">;</span>
    312. 

  312. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br></div></div><h2 id="eslint-的使用"><a href="#eslint-的使用" class="header-anchor">#</a> ESLint 的使用</h2> <p>ESLint 是一个语法规则和代码风格的检查工具，可以用来保证写出语法正确、风格统一的代码。</p> <p>首先，安装 ESLint。</p> <div class="language-bash line-numbers-mode"><pre class="language-bash"><code>$ <span class="token function">npm</span> i <span class="token parameter variable">-g</span> eslint
    313. 

  313. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><p>然后，安装 Airbnb 语法规则，以及 import、a11y、react 插件。</p> <div class="language-bash line-numbers-mode"><pre class="language-bash"><code>$ <span class="token function">npm</span> i <span class="token parameter variable">-g</span> eslint-config-airbnb
    314. 

  314. $ <span class="token function">npm</span> i <span class="token parameter variable">-g</span> eslint-plugin-import eslint-plugin-jsx-a11y eslint-plugin-react
    315. 

  315. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><p>最后，在项目的根目录下新建一个<code>.eslintrc</code>文件，配置 ESLint。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token punctuation">{</span>
    316. 

  316.   <span class="token string-property property">&quot;extends&quot;</span><span class="token operator">:</span> <span class="token string">&quot;eslint-config-airbnb&quot;</span>
    317. 

  317. <span class="token punctuation">}</span>
    318. 

  318. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><p>现在就可以检查，当前项目的代码是否符合预设的规则。</p> <p><code>index.js</code>文件的代码如下。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">var</span> unusued <span class="token operator">=</span> <span class="token string">'I have no purpose!'</span><span class="token punctuation">;</span>
    319. 

  319. 

  320. <span class="token keyword">function</span> <span class="token function">greet</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    321. 

  321.     <span class="token keyword">var</span> message <span class="token operator">=</span> <span class="token string">'Hello, World!'</span><span class="token punctuation">;</span>
    322. 

  322.     <span class="token function">alert</span><span class="token punctuation">(</span>message<span class="token punctuation">)</span><span class="token punctuation">;</span>
    323. 

  323. <span class="token punctuation">}</span>
    324. 

  324. 

  325. <span class="token function">greet</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    326. 

  326. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br></div></div><p>使用 ESLint 检查这个文件，就会报出错误。</p> <div class="language-bash line-numbers-mode"><pre class="language-bash"><code>$ eslint index.js
    327. 

  327. index.js
    328. 

  328.   <span class="token number">1</span>:1  error  Unexpected var, use <span class="token builtin class-name">let</span> or const instead          no-var
    329. 

  329.   <span class="token number">1</span>:5  error  unusued is defined but never used                 no-unused-vars
    330. 

  330.   <span class="token number">4</span>:5  error  Expected indentation of <span class="token number">2</span> characters but found <span class="token number">4</span>  indent
    331. 

  331.   <span class="token number">4</span>:5  error  Unexpected var, use <span class="token builtin class-name">let</span> or const instead          no-var
    332. 

  332.   <span class="token number">5</span>:5  error  Expected indentation of <span class="token number">2</span> characters but found <span class="token number">4</span>  indent
    333. 

  333. 

  334. ✖ <span class="token number">5</span> problems <span class="token punctuation">(</span><span class="token number">5</span> errors, <span class="token number">0</span> warnings<span class="token punctuation">)</span>
    335. 

  335. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br></div></div><p>上面代码说明，原文件有五个错误，其中两个是不应该使用<code>var</code>命令，而要使用<code>let</code>或<code>const</code>；一个是定义了变量，却没有使用；另外两个是行首缩进为 4 个空格，而不是规定的 2 个空格。</p></div></div>  <div class="page-edit"><div class="edit-link"><a href="https://github.com/heBody/blog/edit/master/docs/《ES6 教程》笔记/25.编程风格.md" target="_blank" rel="noopener noreferrer">编辑</a> <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></div> <div class="tags"><a href="/blog/tags/?tag=ES6" title="标签">#ES6</a></div> <div class="last-updated"><span class="prefix">上次更新:</span> <span class="time">2022/12/14, 19:36:42</span></div></div> <div class="page-nav-wapper"><div class="page-nav-centre-wrap"><a href="/blog/pages/a79ca2e64ceae213/" class="page-nav-centre page-nav-centre-prev"><div class="tooltip">Module 的加载实现</div></a> <a href="/blog/pages/32c35f7651d6e58e/" class="page-nav-centre page-nav-centre-next"><div class="tooltip">读懂 ECMAScript 规格</div></a></div> <div class="page-nav"><p class="inner"><span class="prev">
    336. 

  336.         ←
    337. 

  337.         <a href="/blog/pages/a79ca2e64ceae213/" class="prev">Module 的加载实现</a></span> <span class="next"><a href="/blog/pages/32c35f7651d6e58e/">读懂 ECMAScript 规格</a>→
    338. 

  338.       </span></p></div></div></div> <div class="article-list"><div class="article-title"><a href="/blog/archives/" class="iconfont icon-bi">最近更新</a></div> <div class="article-wrapper"><dl><dd>01</dd> <dt><a href="/blog/pages/922650/"><div>
    339. 

  339.             Git修改分支名
    340. 

  340.             <!----></div></a> <span class="date">08-11</span></dt></dl><dl><dd>02</dd> <dt><a href="/blog/pages/55f894/"><div>
    341. 

  341.             CSS给table的tbody添加滚动条
    342. 

  342.             <!----></div></a> <span class="date">06-29</span></dt></dl><dl><dd>03</dd> <dt><a href="/blog/pages/829589/"><div>
    343. 

  343.             我做了一个手写春联小网页，祝大家虎年暴富
    344. 

  344.             <span class="title-tag">
    345. 

  345.               原创
    346. 

  346.             </span></div></a> <span class="date">01-28</span></dt></dl> <dl><dd></dd> <dt><a href="/blog/archives/" class="more">更多文章&gt;</a></dt></dl></div></div></main></div> <div class="footer"><div class="icons"><a href="mailto:30363811@qq.com" title="发邮件" target="_blank" class="iconfont icon-youjian"></a><a href="https://github.com/heBody" title="GitHub" target="_blank" class="iconfont icon-github"></a><a href="https://music.163.com/#/playlist?id=755597173" title="听音乐" target="_blank" class="iconfont icon-erji"></a></div> 
    347. 

  347.   Theme by
    348. 

  348.   <a href="https://github.com/xugaoyi/vuepress-theme-vdoing" target="_blank" title="本站主题">Vdoing</a> 
    349. 

  349.     | Copyright © 2019-2022
    350. 

  350.     <span>Evan Xu | <a href="https://github.com/heBody/blob/master/LICENSE" target="_blank">MIT License</a></span></div> <div class="buttons"><div title="返回顶部" class="button blur go-to-top iconfont icon-fanhuidingbu" style="display:none;"></div> <div title="去评论" class="button blur go-to-comment iconfont icon-pinglun" style="display:none;"></div> <div title="主题模式" class="button blur theme-mode-but iconfont icon-zhuti"><ul class="select-box" style="display:none;"><li class="iconfont icon-zidong">
    351. 

  351.           跟随系统
    352. 

  352.         </li><li class="iconfont icon-rijianmoshi">
    353. 

  353.           浅色模式
    354. 

  354.         </li><li class="iconfont icon-yejianmoshi">
    355. 

  355.           深色模式
    356. 

  356.         </li><li class="iconfont icon-yuedu">
    357. 

  357.           阅读模式
    358. 

  358.         </li></ul></div></div> <!----> <!----> <!----></div><div class="global-ui"><div></div></div></div>
    359. 

  359.     <script src="/blog/assets/js/app.b419507c.js" defer></script><script src="/blog/assets/js/2.602aac03.js" defer></script><script src="/blog/assets/js/111.33bbfeaf.js" defer></script>
    360. 

  360.   </body>
    361. 

  361. </html>
    362.