Upgrade to Pro — share decks privately, control downloads, hide ads and more …

∞ things I didn’t know about HTML, CSS, and Jav...

Sponsored · SiteGround - Reliable hosting with speed, security, and support you can count on. →
Avatar for Mathias Bynens Mathias Bynens
March 01, 2014
Programming
3.9k
11

∞ things I didn’t know about HTML, CSS, and JavaScript @ Kod.io 2014

Slides for my talk on random web development fun facts at Kod.io 2014.

Avatar for Mathias Bynens

Mathias Bynens

March 01, 2014

More Decks by Mathias Bynens

See All by Mathias Bynens
V8 internals for JavaScript developers @ Fronteers 2018
Avatar for Mathias Bynens mathiasbynens
3
540
V8 internals for JavaScript developers
Avatar for Mathias Bynens mathiasbynens
2
1.1k
What’s new in ES2018?
Avatar for Mathias Bynens mathiasbynens
2
160
V8 internals for JavaScript developers
Avatar for Mathias Bynens mathiasbynens
1
200
Preventing timing attacks on the web @ Fronteers Jam 2016
Avatar for Mathias Bynens mathiasbynens
4
280
Front-End Performance: The Dark Side @ ColdFront Conference 2016
Avatar for Mathias Bynens mathiasbynens
1
530
Hacking with Unicode in 2016
Avatar for Mathias Bynens mathiasbynens
15
15k
Front-End Performance: The Dark Side @ Fronteers Spring Conference 2016
Avatar for Mathias Bynens mathiasbynens
16
57k
3.14 things I didn’t know about CSS @ CSSConf.asia 2015
Avatar for Mathias Bynens mathiasbynens
4
1.2k

Other Decks in Programming

See All in Programming
RTSPクライアントを自作してみた話
Avatar for simotin13 simotin13
0
400
軽量Java基盤の設計 DIコンテナに頼らない、長期保守と1秒起動の実現 JJUG CCC 2026 Spring
Avatar for Masaaki Takahashi macha64
0
290
権限チェックの一貫性を型で守る TypeScript による多層防御
Avatar for aster-mnch (kitagawa) mnch
4
1k
Old Dog, New Tricks: The Java 25 Reinvention - JNation
Avatar for A N M Bazlur Rahman bazlur_rahman
0
140
Inside Stream API
Avatar for Yuichi.Sakuraba skrb
1
480
tsserverとは何だったのか、これからどうなるのか
Avatar for Ryota Nakamura nowaki28
1
430
タクシーアプリ『GO』の バックエンド開発のおける AI利活用と若者のすべて
Avatar for Kazuhiko Yamashita pyama86
3
1.8k
Moments When Things Go Wrong
Avatar for Aurimas Liutikas aurimas
3
130
さぁV100、メモリをお食べ・・・
Avatar for nilpe nilpe
0
120
New "Type" system on PicoRuby
Avatar for pocke pocke
1
400
DynamoDBには集計系のクエリがないけどなんとかしたい
Avatar for 村上優稀 musan
1
110
inferと仲良くなる10分間
Avatar for ryokatsuse ryokatsuse
1
300

Featured

See All Featured
Facilitating Awesome Meetings
Avatar for Lara Hogan lara
57
6.9k
Effective software design: The role of men in debugging patriarchy in IT @ Voxxed Days AMS
Avatar for Kenny Baas-Schwegler baasie
0
370
Efficient Content Optimization with Google Search Console & Apps Script
Avatar for Katarina Dahlin katarinadahlin
PRO
1
580
Docker and Python
Avatar for Tania Allard trallard
47
3.9k
コードの90%をAIが書く世界で何が待っているのか / What awaits us in a world where 90% of the code is written by AI
Avatar for r-kagaya rkaga
61
44k
GraphQLとの向き合い方2022年版
Avatar for Yosuke Kurami quramy
50
15k
svc-hook: hooking system calls on ARM64 by binary rewriting
Avatar for Akira Moroo retrage
2
280
AI in Enterprises - Java and Open Source to the Rescue
Avatar for ivargrimstad ivargrimstad
0
1.3k
Navigating Team Friction
Avatar for Lara Hogan lara
192
16k
The agentic SEO stack - context over prompts
Avatar for schlessera schlessera
0
790
Winning Ecommerce Organic Search in an AI Era - #searchnstuff2025
Avatar for Aleyda Solis aleyda
1
2k
Making the Leap to Tech Lead
Avatar for Ryan Cromwell cromwellryan
135
9.9k

Transcript

  1. @mathias · #kodio_2014 Ten things I didn’t know about HTML

  2. @mathias

  3. Ten things I didn’t know about HTML @mathias · #kodio_2014

  4. ∞ things I didn’t know about HTML, CSS & JavaScript

    @mathias · #kodio_2014

  5. Back to the ’90s kickin’ it old skool

  6. None

  7. Background colors <body bgcolor="pink"></body>

  8. Background colors <body bgcolor="pink"></body>

  9. Background colors <body bgcolor="#ffc0cb"></body>

  10. Background colors <body bgcolor="ffc0cb"></body>

  11. Background colors <body bgcolor="#f3f"></body> " #FF33FF

  12. Background colors <body bgcolor="f3f"></body> " #0F030F

  13. Background colors <body bgcolor="sick"></body> " #00C000

  14. Background colors <body bgcolor="MrT"></body> " #000000

  15. Background colors <body bgcolor="chucknorris"></body> " #C00000

  16. Background colors <body bgcolor="crap"></body> " #C0A000

  17. Background colors <body bgcolor="!"></body> " #000000

  18. Background colors <body bgcolor="kodio"></body> " #00D000

  19. Background colors http://mths.be/bgcolor

  20. Background colors http://mths.be/bgcolor

  21. “Valid HTML” conformance criteria

  22. Document Type Definition

  23. DTD <head> <p>Lorem ipsum.</p> </head>

  24. DTD <kitchensink>

  25. DTD fail <input type="date" placeholder="foo">

  26. DTD fail <input type="date" placeholder="foo"> <table> <tr><td>foo</td></tr> <tr><td colspan="2">bar</td></tr> </table>

  27. DTD fail <input type="date" placeholder="foo"> → can still be checked

    by a computer <table> <tr><td>foo</td></tr> <tr><td colspan="2">bar</td></tr> </table>

  28. Computer says no <img src="foo.png" alt=""> <time datetime="2013-10-03">LOL</time> <blockquote>not a

    quote</blockquote>

  29. Computer says no <img src="foo.png" alt=""> → can only be

    checked by a human <time datetime="2013-10-03">LOL</time> <blockquote>not a quote</blockquote>

  30. Take-away Don’t obsess about HTML validation. • not the whole

    story • validators have bugs, too Functionality trumps validation anyway.
 <meta http-equiv="X-UA-Compatible" content="IE=edge">

  31. Character references aka. “entities”

  32. Character references <!-- valid and reliable: --> <p>foo &amp; bar</p>

    <!-- renders as “foo & bar” -->

  33. ;

  34. github:twbs/bootstrap#3057

  35. github:twbs/bootstrap#3057

  36. ;

  37. ; PRETENDS TO BE OPTIONAL BREAKS STUFF WHEN OMITTED

  38. Character references <!-- valid and reliable: --> <p>foo &amp; bar</p>

    <!-- renders as “foo & bar” -->

  39. Character references <!-- invalid, but reliable: --> <p>foo &amp bar</p>

    <!-- renders as “foo & bar” -->

  40. Character references <!-- invalid, and confusing: --> <p title="foo&ampbar"> foo&ampbar

    </p> <!-- title renders as “foo&ampbar” --> <!-- text renders as “foo&bar” -->

  41. Character references <!-- valid and reliable: --> <p>foo & bar</p>

    <!-- renders as “foo & bar” --> http://mths.be/bdu

  42. Character references <!-- valid and reliable: --> <p>foo &gt; bar</p>

    <!-- renders as “foo > bar” -->

  43. Character references <!-- invalid, but reliable: --> <p>foo &gt bar</p>

    <!-- renders as “foo > bar” -->

  44. Character references <!-- invalid, and confusing: --> <p title="foo&gtbar"> foo&gtbar

    </p> <!-- title renders as “foo&gtbar” --> <!-- text renders as “foo>bar” -->

  45. Character references <!-- valid and reliable: --> <p>foo > bar</p>

    <!-- renders as “foo > bar” -->

  46. Character references <p>foo&#x85;bar</p> <!-- which symbol is this? --> <!--

    how will it render? -->

  47. Character references <p>foo&#x85;bar</p> <!-- which symbol is this? --> <!--

    how will it render? -->

  48. &#x85; is U+0085, right?

  49. &#x85; is U+0085, right? ✘

  50. Nope, not in HTML!

  51. Nope, not in HTML!

  52. …but it is in XHTML

  53. Character references

  54. Tags

  55. Valid HTML <!DOCTYPE html>
 <html>
 <head>
 <title>Foo</title>
 </head>
 <body>
 …


    </body>
 </html>

  56. Valid HTML <!DOCTYPE html>
 <html>
 <head>
 <title>Foo</title>
 </head>
 <body>
 …


    </body>
 </html>

  57. Valid HTML <!DOCTYPE html>
 <html>
 <head>
 <title>Huh?</title>
 <body>
 …


  58. Valid HTML <!DOCTYPE html>
 <html>
 <head>
 <title>Huh?</title>
 <body>
 …


  59. Valid HTML <!DOCTYPE html>
 <title>lolwut</title>
 …


  60. None
  61. None

  62. ^ n FTFY

  63. Using CSS without HTML

  64. None
  65. None

  66. CSS without HTML $ curl -i http://mathiasbynens.be/demo/css-without-html HTTP/1.1 200 OK

    Date: Wed, 03 Oct 2013 13:33:37 GMT Link: <css-without-html.css>;rel=stylesheet Content-Length: 0 Content-Type: text/html; charset=UTF-8 http://mths.be/bpe

  67. CSS without HTML $ curl -i http://mathiasbynens.be/demo/css-without-html HTTP/1.1 200 OK

    Date: Wed, 03 Oct 2013 13:33:37 GMT Link: <css-without-html.css>;rel=stylesheet Content-Length: 0 Content-Type: text/html; charset=UTF-8 http://mths.be/bpe
  68. None

  69. Font family names

  70. CSS html {
 font-family: 'Comic Sans MS';
 } “If there’s

    whitespace in the font family name, it must be quoted.”

  71. CSS html {
 font-family: Comic Sans MS;
 } “If there’s

    whitespace in the font family name, it must be quoted.” http://mths.be/bft

  72. CSS html {
 font-family: 456bereastreet;
 }

  73. CSS html {
 font-family: 456bereastreet;
 }

  74. CSS html {
 font-family: \34 56bereastreet;
 }

  75. CSS html {
 font-family: \34 56bereastreet;
 }

  76. CSS html {
 font-family: '456bereastreet';
 }

  77. CSS http://mths.be/bjm

  78. Attribute values

  79. Attribute values <a href="foo">…</a> <style> a[href="foo"] { background: hotpink; }

    </style>

  80. Attribute values <a href=foo>…</a> <style> a[href=foo] { background: hotpink; }

    </style>

  81. Attribute values <a href=foo|bar>…</a> <style> a[href=foo|bar] { background: hotpink; }

    </style>

  82. Attribute values <a href=foo|bar>…</a> <style> a[href=foo|bar] { background: hotpink; }

    </style>

  83. Attribute values <a href=foo|bar>…</a> <style> a[href="foo|bar"] { background: hotpink; }

    </style> http://mths.be/bal

  84. Attribute values http://mths.be/bjn

  85. Handling user input

  86. http://mths.be/bqv

  87. http://mths.be/bqv

  88. Characters in JS

  89. JavaScript string length >> 'A'.length // U+0041 1 >> 'A'

    == '\u0041' true >> 'B'.length // U+0042 1 >> 'B' == '\u0042' true

  90. String length ≠ char count >> 'A'.length // U+1D400 2

    >> 'A' == '\uD835\uDC00' true >> 'B'.length // U+1D401 2 >> 'B' == '\uD835\uDC01' true http://mths.be/bed

  91. Surrogate pairs // for non-BMP code points (> 0xFFFF) function

    getSurrogates(codePoint) { var high = Math.floor((codePoint - 0x10000) / 0x400) + 0xD800; var low = (codePoint - 0x10000) % 0x400 + 0xDC00; return [ high, low ]; } ! function getCodePoint(high, low) { var codePoint = (high - 0xD800) * 0x400 + low - 0xDC00 + 0x10000; return codePoint; } ! >> getSurrogates('A'); // U+1D400 [ 0xD835, 0xDC00 ] >> getCodePoint(0xD835, 0xDC00); 0x1D400 http://mths.be/bed

  92. JS string character count function countSymbols(string) { return punycode.ucs2.decode(string).length; }

    ! >> countSymbols('A') // U+0041 1 >> countSymbols('A') // U+1D400 1 http://mths.be/punycode

  93. JS variable names

  94. Which is invalid? var H ̹̙̦̮͉̩̗̗ ͧ̇̏̊̾ Eͨ͆͒̆ͮ̃ ͏̷̮̣̫̤̣Cͯ̂͐ ͏̨̛͔̦̟͈̻O

    ̜͎͍͙͚̬̝̣ ̽ͮ͐͗̀ͤ̍̀ ͢ M̴̡̲̭͍͇̼̟̯̦ ̉̒͠ Ḛ̛̙̞̪̗ ͥ ͤͩ̾͑̔͐ ͅ Ṯ̴̷̷̗̼͍ ̿̿̓̽͐ H ̙̙ ̔̄ ͜ ; var "_ಠಠ_"; var ໦ϗ îਓƎ ℵೋീΔେ; var ʃː λ ˀπ ᐩᐨᐟᑉᐦᐸᐳ\u200C; var a; http://mths.be/ber

  95. ♥ JS var H ̹̙̦̮͉̩̗̗ ͧ̇̏̊̾ Eͨ͆͒̆ͮ̃ ͏̷̮̣̫̤̣Cͯ̂͐ ͏̨̛͔̦̟͈̻O ̜͎͍͙͚̬̝̣

    ̽ͮ͐͗̀ͤ̍̀ ͢ M̴̡̲̭͍͇̼̟̯̦ ̉̒͠ Ḛ̛̙̞̪̗ ͥ ͤͩ̾͑̔͐ ͅ Ṯ̴̷̷̗̼͍ ̿̿̓̽͐ H ̙̙ ̔̄ ͜ ; // valid var !_ಠಠ_!; // valid var ໦ϗ îਓƎ ℵೋീΔେ; // valid var ʃː λ ˀπ ᐩᐨᐟᑉᐦᐸᐳ\u200C; // valid var a; // syntax error http://mths.be/ber

  96. /^(?!(?:do|if|in|for|let|new|try|var|case|else| enum|eval|false|null|this|true|void|with|break| catch|class|const|super|throw|while|yield|delete| export|import|public|return|static|switch|typeof| default|extends|finally|package|private|continue| debugger|function|arguments|interface|protected| implements|instanceof)$)[$A-Z\_a-z\xaa\xb5\xba \xc0-\xd6\xd8-\xf6\xf8-\u02c1\u02c6-\u02d1\u02e0- \u02e4\u02ec\u02ee\u0370- \u0374\u0376\u0377\u037a-\u037d\u0386\u0388-

    \u038a\u038c\u038e-\u03a1\u03a3-\u03f5\u03f7- \u0481\u048a-\u0527\u0531-\u0556\u0559\u0561- \u0587\u05d0-\u05ea\u05f0-\u05f2\u0620-\u064a

  97. \u20f0\u2cef-\u2cf1\u2d7f\u2de0-\u2dff\u302a- \u302f\u3099\u309a\ua620-\ua629\ua66f\ua674- \ua67d\ua69f\ua6f0\ua6f1\ua802\ua806\ua80b\ua823- \ua827\ua880\ua881\ua8b4-\ua8c4\ua8d0- \ua8d9\ua8e0-\ua8f1\ua900-\ua909\ua926-\ua92d \ua947-\ua953\ua980-\ua983\ua9b3-\ua9c0\ua9d0- \ua9d9\uaa29-\uaa36\uaa43\uaa4c\uaa4d\uaa50- \uaa59\uaa7b\uaab0\uaab2-\uaab4\uaab7\uaab8\uaabe \uaabf\uaac1\uaaeb-\uaaef\uaaf5\uaaf6\uabe3- \uabea\uabec\uabed\uabf0-\uabf9\ufb1e\ufe00-

    \ufe0f\ufe20-\ufe26\ufe33\ufe34\ufe4d-\ufe4f \uff10-\uff19\uff3f]*$/

  98. JS variable names http://mths.be/bjo

  99. Questions? @mathias