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∞ things I didn’t know about HTML, CSS, and Jav...
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Mathias Bynens
March 01, 2014
Programming
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3.8k
∞ 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.
Mathias Bynens
March 01, 2014
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Transcript
@mathias · #kodio_2014 Ten things I didn’t know about HTML
@mathias
Ten things I didn’t know about HTML @mathias · #kodio_2014
∞ things I didn’t know about HTML, CSS & JavaScript
@mathias · #kodio_2014
Back to the ’90s kickin’ it old skool
None
Background colors <body bgcolor="pink"></body>
Background colors <body bgcolor="pink"></body>
Background colors <body bgcolor="#ffc0cb"></body>
Background colors <body bgcolor="ffc0cb"></body>
Background colors <body bgcolor="#f3f"></body> " #FF33FF
Background colors <body bgcolor="f3f"></body> " #0F030F
Background colors <body bgcolor="sick"></body> " #00C000
Background colors <body bgcolor="MrT"></body> " #000000
Background colors <body bgcolor="chucknorris"></body> " #C00000
Background colors <body bgcolor="crap"></body> " #C0A000
Background colors <body bgcolor="!"></body> " #000000
Background colors <body bgcolor="kodio"></body> " #00D000
Background colors http://mths.be/bgcolor
Background colors http://mths.be/bgcolor
“Valid HTML” conformance criteria
Document Type Definition
DTD <head> <p>Lorem ipsum.</p> </head>
DTD <kitchensink>
DTD fail <input type="date" placeholder="foo">
DTD fail <input type="date" placeholder="foo"> <table> <tr><td>foo</td></tr> <tr><td colspan="2">bar</td></tr> </table>
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>
Computer says no <img src="foo.png" alt=""> <time datetime="2013-10-03">LOL</time> <blockquote>not a
quote</blockquote>
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>
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">
Character references aka. “entities”
Character references <!-- valid and reliable: --> <p>foo & bar</p>
<!-- renders as “foo & bar” -->
;
github:twbs/bootstrap#3057
github:twbs/bootstrap#3057
;
; PRETENDS TO BE OPTIONAL BREAKS STUFF WHEN OMITTED
Character references <!-- valid and reliable: --> <p>foo & bar</p>
<!-- renders as “foo & bar” -->
Character references <!-- invalid, but reliable: --> <p>foo & bar</p>
<!-- renders as “foo & bar” -->
Character references <!-- invalid, and confusing: --> <p title="foo&bar"> foo&bar
</p> <!-- title renders as “foo&bar” --> <!-- text renders as “foo&bar” -->
Character references <!-- valid and reliable: --> <p>foo & bar</p>
<!-- renders as “foo & bar” --> http://mths.be/bdu
Character references <!-- valid and reliable: --> <p>foo > bar</p>
<!-- renders as “foo > bar” -->
Character references <!-- invalid, but reliable: --> <p>foo > bar</p>
<!-- renders as “foo > bar” -->
Character references <!-- invalid, and confusing: --> <p title="foo>bar"> foo>bar
</p> <!-- title renders as “foo>bar” --> <!-- text renders as “foo>bar” -->
Character references <!-- valid and reliable: --> <p>foo > bar</p>
<!-- renders as “foo > bar” -->
Character references <p>foo…bar</p> <!-- which symbol is this? --> <!--
how will it render? -->
Character references <p>foo…bar</p> <!-- which symbol is this? --> <!--
how will it render? -->
… is U+0085, right?
… is U+0085, right? ✘
Nope, not in HTML!
Nope, not in HTML!
…but it is in XHTML
Character references
Tags
Valid HTML <!DOCTYPE html> <html> <head> <title>Foo</title> </head> <body> …
</body> </html>
Valid HTML <!DOCTYPE html> <html> <head> <title>Foo</title> </head> <body> …
</body> </html>
Valid HTML <!DOCTYPE html> <html> <head> <title>Huh?</title> <body> …
Valid HTML <!DOCTYPE html> <html> <head> <title>Huh?</title> <body> …
Valid HTML <!DOCTYPE html> <title>lolwut</title> …
None
None
^ n FTFY
Using CSS without HTML
None
None
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
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
None
Font family names
CSS html { font-family: 'Comic Sans MS'; } “If there’s
whitespace in the font family name, it must be quoted.”
CSS html { font-family: Comic Sans MS; } “If there’s
whitespace in the font family name, it must be quoted.” http://mths.be/bft
CSS html { font-family: 456bereastreet; }
CSS html { font-family: 456bereastreet; }
CSS html { font-family: \34 56bereastreet; }
CSS html { font-family: \34 56bereastreet; }
CSS html { font-family: '456bereastreet'; }
CSS http://mths.be/bjm
Attribute values
Attribute values <a href="foo">…</a> <style> a[href="foo"] { background: hotpink; }
</style>
Attribute values <a href=foo>…</a> <style> a[href=foo] { background: hotpink; }
</style>
Attribute values <a href=foo|bar>…</a> <style> a[href=foo|bar] { background: hotpink; }
</style>
Attribute values <a href=foo|bar>…</a> <style> a[href=foo|bar] { background: hotpink; }
</style>
Attribute values <a href=foo|bar>…</a> <style> a[href="foo|bar"] { background: hotpink; }
</style> http://mths.be/bal
Attribute values http://mths.be/bjn
Handling user input
http://mths.be/bqv
http://mths.be/bqv
Characters in JS
JavaScript string length >> 'A'.length // U+0041 1 >> 'A'
== '\u0041' true >> 'B'.length // U+0042 1 >> 'B' == '\u0042' true
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
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
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
JS variable names
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
♥ 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
/^(?!(?: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
\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]*$/
JS variable names http://mths.be/bjo
Questions? @mathias