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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>So, what’s new in ES2020? • Christophe Porteneuve @ Confoo Montréal 2018</title>
<meta name="description" content="ES2015 is awesome and ES2017 is super cool, but tons of interesting stuff is still incoming… most of which we can already play with!">
<meta name="author" content="Christophe Porteneuve">
<meta name="apple-mobile-web-app-capable" content="yes" />
<meta name="apple-mobile-web-app-status-bar-style" content="black-translucent" />
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
<link href='css/fonts.css' rel='stylesheet' type='text/css'>
<link rel="stylesheet" href="css/reveal.css">
<link rel="stylesheet" href="css/animate.min.css">
<link rel="stylesheet" href="css/theme/sky.css" id="theme-basis">
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<script>
window.dataLayer = window.dataLayer || [];
function gtag(){dataLayer.push(arguments);}
gtag('js', new Date());
gtag('config', 'UA-43650325-23');
</script>
</head>
<body id="prioFix">
<div class="reveal">
<!-- Any section element inside of this container is displayed as a slide -->
<div class="slides">
<section id="mainTitle">
<h1>
<span>So, what’s new in</span> ES2020?
</h1>
<p>
<small>A handpicked selection of cool stuff by <a href="http://tddsworld.com/">Christophe Porteneuve</a> at <a href="https://confoo.ca/en">Confoo Montréal 2018</a></small><br/>
<small><a href="https://joind.in/talk/e8ec5">https://joind.in/talk/e8ec5</a></small>
</p>
</section>
<section id="whoami">
<h2>whoami</h2>
<pre><code data-trim class="language-js">
const christophe = {
family: { wife: 'Élodie', son: 'Maxence', [Symbol.guess]: '*Shh*' },
city: 'Paris, FR',
company: 'Delicious Insights',
firstTimeInMontreal: true,
lastTimeInMontreal: Symbol.noWay,
trainings: [
'Web Apps Modernes', 'Node.js', 'Git Total',
'ES Total', 'Webpack'
],
webSince: 1995,
claimsToFame: [
'Prototype.js',
'Ruby On Rails',
'Prototype and Script.aculo.us',
'Paris Web',
'NodeSchool Paris'
],
}
</code></pre>
</section>
<section data-state="theme-color-blue-yellow">
<section id="tc39">
<h1>ES2020?!</h1>
<h3>ECMA, TC39, ECMAScript and JavaScript</h3>
</section>
<section>
<h2>ECMA and the TC39</h2>
<p>ECMA is an international standards body<br/>
(much like ISO, IETF, W3C or WHATWG, for instance)</p>
<p>ES = ECMAScript. The official standard for JavaScript*</p>
<p>
TC39 = Technical Committee 39. Caretaker for many standards:<br/>
ECMAScript (ECMA-262), Intl (ECMA-402), JSON (ECMA-404), etc.
</p>
<footer>* Which happens to be, these days, a U.S. trademark held by Oracle® Corporation. Yeah. I know.</footer>
</section>
<section>
<h2>The TC39 process</h2>
<p>Meetings at various locations every 2 months. A yearly release, usually in June.</p>
<p>“ES6” ➡️ ES2015, “ES7” ➡️ ES2016,<br/>and now we say ES2017, etc.</p>
<p>It’s all <a href="https://github.com/tc39">public</a>.</p>
</section>
<section>
<h2>The TC39 process</h2>
<p>Language proposals go through <a href="https://tc39.github.io/process-document/">5 stages</a>:</p>
<table class="condensed">
<thead>
<tr><th>Stage</th><th>Description</th></tr>
</thead>
<tbody>
<tr>
<th>0 Strawman</th>
<td>“It’d be dandy if we had a unicorn operator (🦄) to…”</td>
</tr>
<tr class="fragment">
<th>1 Proposal</th>
<td>A TC39 member “champions” the proposal. General API look and feel hammered down, and many/most cross-cutting concerns addressed.</td>
</tr>
<tr class="fragment">
<th>2 Draft</th>
<td>Initial spec text, covers all critical aspects and technical semantics.</td>
</tr>
<tr class="fragment">
<th>3 Candidate</th>
<td>Spec complete, verified by appropriate reviewers and greenlighted. API finalized, no stone left unturned.</td>
</tr>
<tr class="fragment">
<th>4 Finished</th>
<td>Full Test262 coverage, 2+ shipping implementations (e.g. V8 + SpiderMonkey), significant real-world usage feedback, Spec Editor imprimatur. Usually goes into the next feature freeze (January or March).</td>
</tr>
</tbody>
</table>
</section>
</section>
<section data-state="theme-color-silver-green">
<section id="es2017">
<h1>ES2017</h1>
<h3>(in case you missed it…)</h3>
</section>
<section id="trailing-commas">
<h2>Moar trailing commas!</h2>
<h4><a href="https://github.com/tc39/proposal-trailing-function-commas">spec</a></h4>
<div class="two-columns">
<div>
<pre><code class="language-js" data-trim data-keep-tags="u">
function yowza(
key,
increment<u>,</u>
) {
// …
}
</code></pre>
</div>
<div>
<pre><code class="language-js" data-trim data-keep-tags="u">
const yowza = (
key,
increment<u>,</u>
) => …
</code></pre>
<pre><code class="language-js" data-trim data-keep-tags="u">
yowza(
'itemScore',
+10<u>,</u>
)
</code></pre>
</div>
</div>
<p>Remember: ES5 (2009…) already let you do these:</p>
<div class="two-columns">
<div>
<pre><code class="language-js" data-trim data-keep-tags="u">
const roiDeLaClasse = {
first: 'Georges',
last: 'Abitbol'<u>,</u>
}
</code></pre>
</div>
<div>
<pre><code class="language-js" data-trim data-keep-tags="u">
const courses = [
'ES Total',
'Webpack'<u>,</u>
]
</code></pre>
</div>
</div>
<footer>Prettier : <code>trailingCommas: 'all'</code></footer>
</section>
<section id="async-await">
<h2><code>async</code> / <code>await</code></h2>
<h4 lang="en"><a href="https://github.com/tc39/ecmascript-asyncawait">Async functions</a></h4>
<pre><code class="language-js" data-trim data-keep-tags="u">
<u>async</u> function createEntry(req, res) {
<u>try</u> {
const urlReq = <u>await</u> fetch(req.body.url)
const html = <u>await</u> urlReq.text()
const analysis = unfluff(html)
const entry = <u>await</u> Entry.post({ … })
// …
} <u>catch</u> (err) {
req.flash('error', `Une erreur est survenue en traitant cette URL : ${err.message}`)
res.redirect('/entries/new')
}
}
</code></pre>
<pre><code class="language-js" data-trim data-keep-tags="u">
const [tags, entryCount, entries] = <u>await</u> Promise.all([
Entry.tags(), Entry.count(), Entry.getEntries(req.query),
])
</code></pre>
</section>
</section> <!-- #es2017 -->
<section data-state="theme-color-forest-yellow">
<section id="es2018">
<h1>ES0218</h1>
<h4>(As per feature freezing in January 2018, may still expand)</h4>
</section>
<section id="async-iteration">
<h2>Async iteration</h2>
<h4><a href="https://github.com/tc39/proposal-async-iteration">Spec</a></h4>
<p>Easily queue / loop over async requests.<br/>Async iterables, iterators and generators use promises, so <code>async</code>/<code>await</code> work seamlessly with it.</p>
<div class="two-columns with-code">
<div>
<pre><code class="language-js" data-trim data-keep-tags="u">
for <u>await</u> (const line of readLines(filePath)) {
console.log(line)
}
</code></pre>
</div>
<div>
<pre><code class="language-js" data-trim data-keep-tags="u">
<u>async function*</u> readLines(path) {
let file = await fileOpen(path);
try {
while (!file.EOF) {
yield await file.readLine();
}
} finally {
await file.close();
}
}
</code></pre>
</div>
</div>
<footer>
Native: FF 57+, Ch63+, SF TP. No Edge or Node yet.<br/>
Babel: <code>preset-env</code> (<code>shippedProposals</code>) / <code>plugin-transform-async-generator-functions</code>
</footer>
</section>
<section id="rest-spread-properties">
<h2>Rest / Spread Properties</h2>
<h4><a href="https://github.com/tc39/proposal-object-rest-spread">Spec</a></h4>
<pre><code class="language-js" data-trim data-keep-tags="u">
// nonStandardAction = { type: 'progress', goalId: 1, increment: 2 }
const { type, <u>...</u>payload } = nonStandardAction
// => payload = { goalId: 1, increment: 2 }
</code></pre>
<pre><code class="language-js" data-trim data-keep-tags="u">
function doStuff(url, options = {}) {
const opts = { <u>...</u>DEFAULT_OPTIONS, <u>...</u>options, regular: true }
// …
}
</code></pre>
<pre><code class="language-js" data-trim data-keep-tags="u">
return {
<u>...</u>state,
history: tallyHistory(state),
today: moment().format('YYYY-MM-DD'),
todaysProgress: {},
}
</code></pre>
</section>
<section id="rest-spread-properties-2">
<h2>Rest / Spread Properties</h2>
<h4><a href="https://github.com/tc39/proposal-object-rest-spread">Spec</a></h4>
<p>
This is a new <strong>default</strong> behavior:
you could already implement <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/iterator">custom iterability</a> for your objects.
</p>
<pre><code class="language-js" data-trim data-keep-tags="u">
class SuperDuper {
<u>[Symbol.iterator]()</u> {
// Prep and return an Iterator-compliant object:
return {
<u>next()</u> {
// …
return <u>{ done, value }</u>
}
}
}
}
</code></pre>
<footer>
Native: FF 57+, Ch63+, SF 11.1, Node 8. No Edge yet.<br/>
Babel: <code>preset-env</code> (<code>shippedProposals</code>) / <code>plugin-transform-object-rest-spread</code>
</footer>
</section>
<section id="regexp">
<h2>RegExp extravaganza!</h2>
<h4>
<a href="https://github.com/tc39/proposal-regexp-named-groups">RegExp named capture groups</a>,
<a href="https://github.com/tc39/proposal-regexp-unicode-property-escapes">RegExp Unicode property escapes</a>,<br/>
<a href="https://github.com/tc39/proposal-regexp-lookbehind">RegExp lookbehind assertions</a>,
<a href="https://github.com/tc39/proposal-regexp-dotall-flag">RegExp DotAll flag</a>
</h4>
<p>XRegExp, your days are numbered… 😉</p>
<pre><code class="language-js" data-trim data-keep-tags="u">
const RE_ISO_DATE = /(?<u><year></u>\d{4})-(?<u><month></u>\d{2})-(?<u><day></u>\d{2})/u
console.log(RE_ISO_DATE.exec('2017-10-05')<u>.groups</u>)
// => { year: '2017', month: '10', day: '05' }
'2017-10-05'.replace(RE_ISO_DATE, '<u>$<day></u>/<u>$<month></u>/<u>$<year></u>')
// => '05/10/2017'
const RE_DIGITS = /^<u>\p{Decimal_Number}</u>+$/u
RE_DIGITS.test('𝟏𝟐𝟑𝟜𝟝𝟞𝟩𝟪𝟫𝟬𝟭𝟮𝟯𝟺𝟻𝟼') // => true
const RE_ANYTHING_GOES = /foo.bar/<u>s</u>
RE_ANYTHING_GOES.test('foo\nbar') // => true
</code></pre>
<footer>
Native: Ch64+, SF 11.1 (except lookbehind). No Node, FF or Edge yet.<br/>
Babel: <code>preset-stage-3</code> + <code>plugin-transform-modern-regexp</code>
</footer>
</section>
<section id="es2018-misc">
<h2>Other ES2018 tidbits</h2>
<h4>
<a href="https://github.com/tc39/proposal-promise-finally">Promise#finally</a>,
<a href="https://tc39.github.io/proposal-template-literal-revision/">Template literals revision</a>
</h4>
<p>Always-invoked callback, much like <code>try…finally…</code> :</p>
<pre><code class="language-js" data-trim data-keep-tags="u">
fetch('/api/v1/ohai')
.then(…)
.catch(…)
<u>.finally(…)</u>
</code></pre>
<p>Illegal escape sequences in tagged template strings (TTS) don’t break, they only pass the raw string, so you can do this:</p>
<pre><code class="language-js" data-trim data-keep-tags="u">
latex`\unicode` // Despite \un not being a valid Unicode escape
windowsPath`C:\uuu\xxx\088` // Despite \uu, \xx and \08 not being valid escapes
</code></pre>
<footer>
Native: FF58+, Ch63+, SF 11.1. No Edge or Node yet.<br/>
Babel: <code>preset-env</code> (<code>shippedProposals</code>) for Promise#finally. Nothing for revised TTS.<br/>
Also, check out <a href="http://exploringjs.com/es2018-es2019/">this book</a> for great ES2018 explanations.
</footer>
</section>
</section> <!-- #es2018 -->
<section data-state="theme-color-blue-yellow">
<section id="es2019-es2020">
<h1>ES0219 & ES2020</h1>
<h4>chosen bits that’ll probably show up (stages 2–3)</h4>
<footer>(Next to no native support just now, FYI)</footer>
</section>
<section id="class-fields">
<h2>Class Fields</h2>
<h4><a href="https://github.com/tc39/proposal-class-fields">Spec</a></h4>
<pre><code class="language-js" data-trim data-keep-tags="u">
class APIConnector extends Component {
// Public static field
<u>static propTypes =</u> {
apiKey: PropTypes.string.isRequired,
}
// Private (“for real”, a la C++ friend) instance field
<u>#secretToken =</u> null
// Public instance field (equiv. to this.awesome init inside constructor)
<u>awesome =</u> true
// …
}
</code></pre>
<footer>Babel: stage 1 version available still (preset / <code>class-properties</code>), stage 2 WIP</footer>
</section>
<section id="private-methods">
<h2>Private methods and accessors</h2>
<h4><a href="https://github.com/tc39/proposal-private-methods">Spec</a></h4>
<p>Just a follow-up on private fields…</p>
<pre><code class="language-js" data-trim data-keep-tags="u">
class APIConnector {
get <u>#</u>apiToken() {
…
}
set <u>#</u>apiToken(value) {
…
}
<u>#</u>checkConnectivity() {
…
}
}
</code></pre>
</section>
<section id="dynamic-import">
<h2><code>import(…)</code></h2>
<h4><a href="https://github.com/tc39/proposal-dynamic-import">Dynamic import</a></h4>
<p>Lazily import native ESM (dynamic specifier / code splitting). </p>
<pre><code class="language-js" data-trim data-keep-tags="u">
import(`./l10n/${currentUser.locale}`)
.then((locale) => app.l10n.use(locale))
.catch((err) => app.reportError(err))
</code></pre>
<p>As this is Promise-based, you can get even fancier:</p>
<pre><code class="language-js" data-trim data-keep-tags="u">
try {
app.l10n.use(await import(`./l10n/${currentUser.locale}`))
} catch (err) {
app.reportError(err)
}
</code></pre>
<footer>Babel: <code>preset-stage-3</code> / <code>plugin-syntax-dynamic-import</code> (and <code>plugin-dynamic-import-node</code>).<br/>
“Native” with Webpack 2+.</footer>
</section>
<section id="optional-catch-binding">
<h2>Optional catch binding</h2>
<h4><a href="https://github.com/tc39/proposal-optional-catch-binding">spec</a></h4>
<p>Not using the exception? No need to bind it now!</p>
<pre><code class="language-js" data-trim data-keep-tags="u">
try {
return JSON.parse(await readFile(optionalConfigFilePath))
} <u>catch</u> {
return {}
}
</code></pre>
<footer>
Native: FF58, Ch66, SF 11.1.<br/>
Babel: <code>preset-env</code> (with <code>shippedProposals: true</code>)
</footer>
</section>
<section id="throw-expressions">
<h2><code>throw</code> expressions</h2>
<h4><a href="https://github.com/tc39/proposal-throw-expressions">Spec</a></h4>
<p>Not a statement anymore, but an expression. Spares us superfluous function wrapping.</p>
<pre><code class="language-js" data-trim data-keep-tags="u">
function save(fileName = <u>throw</u> new TypeError('File name required')) {
…
}
</code></pre>
<pre><code class="language-js" data-trim data-keep-tags="u">
function getEncoder(encoding) {
// Trigger warning: nested ternaries 😱
const encoder = encoding === 'utf8' ? new UTF8Encoder()
: encoding === 'utf16le' ? new UTF16Encoder(false)
: encoding === 'utf16be' ? new UTF16Encoder(true)
: <u>throw</u> new Error(`Unsupported encoding: ${encoding}`)
…
}
</code></pre>
</section>
<section id="decorators">
<h2>Decorators</h2>
<h4><a href="https://github.com/tc39/proposal-decorators">Spec</a></h4>
<div class="two-columns with-code">
<div>
<pre><code class="language-js" data-trim data-keep-tags="u">
<u>@mixin</u>(SocialNetworkAddictMixin)
class Person {
<u>@deprecate</u>
facepalm() { … }
<u>@throttle</u>('1hr', { leading: true })
checkFacebook() { … }
<u>@memoize</u>('15min')
checkTwitter() { … }
}
</code></pre>
</div>
<div>
<pre><code class="language-js" data-trim data-keep-tags="u">
class Person {
<u>@computedFrom</u>('firstName', 'lastName')
get fullName() {
return `${this.firstName} ${this.lastName}`
}
}
</code></pre>
<pre><code class="language-js" data-trim data-keep-tags="u">
<u>@connect</u>(mapStateToProps, { logOut })
class SettingsScreen extends Component {
<u>@autobind</u>
openGoalAdder() { … }
<u>@override</u>
componentWillReceiveProps() { … }
}
</code></pre>
</div>
</div>
<footer>Babel : stage-1 version in preset, plus legacy plugin. stage-2 WIP.</footer>
</section>
<section id="numeric-separator">
<h2>Numeric separator</h2>
<h4><a href="https://github.com/tc39/proposal-numeric-separator">Spec</a></h4>
<p>Because most major languages have them! 😠</p>
<pre><code class="language-js" data-trim data-keep-tags="u">
const FACTOR = <u>1_000_000_000</u>
const FEE = <u>123_00</u>
const FRACTION = <u>0.000_001</u>
const BITS = <u>0b1010_0001_1000_0101</u>
const FLAG = <u>0xDEAD_BEEF</u>
</code></pre>
<footer>Babel : <code>preset-stage-1</code> (now stage 2, but…), <code>plugin-transform-numeric-separator</code></footer>
</section>
</section> <!-- #es2019 -->
<section data-state="theme-color-silver-green">
<section id="esnext">
<h1>Later</h1>
<h4>(maybe; stage 1)</h4>
</section>
<section id="optional-chaining">
<h2>Taking it easy with <code>null</code> and <code>undefined</code></h2>
<h4>
<a href="https://github.com/tc39/proposal-optional-chaining">Optional Chaining</a>
and
<a href="https://github.com/tc39/proposal-nullish-coalescing">Nullish Coalescing</a>
</h4>
<pre><code class="language-js" data-trim data-keep-tags="u">
// Deep chaining despite missing slots? Hold my 🍺.
const userStreet = user<u>?.</u>address<u>?.</u>street
// Works for indirect indexing too
const userProp = user<u>?.</u>[propName]
// Optional method? There you go.
iterator.return<u>?.</u>()
// Default value IIF null/undefined? Sure thing.
const chunkMode = settings.optimization?.splitChunks?.chunks <u>??</u> 'async'
</code></pre>
<footer>Babel covers optional chaining: <code>preset-stage-1</code> or <code>transform-optional-chaining</code>. WIP on nullish coalescing.</footer>
</section>
<section id="protocols">
<h2>Véritables protocoles</h2>
<h4><a href="https://github.com/michaelficarra/proposal-first-class-protocols">First-class protocols</a></h4>
<div class="two-columns with-code">
<div>
<pre><code class="language-js" data-trim data-keep-tags="u">
<u>protocol</u> RubyStyleEnumerable {
// Symbol(s) to implement per-case
_each
// (Implemented) methods on top of these
cycle (…) { … }
count () { … }
drop (…) { … }
each (…) { … }
map (…) { … }
…
}
</code></pre>
</div>
<div>
<pre><code class="language-js" data-trim data-keep-tags="u">
class Hash <u>implements RubyStyleEnumerable</u> {
// Implement the symbol your way…
[RubyStyleEnumerable._each] () { … }
// …get the rest for free 😉
}
</code></pre>
</div>
</div>
<p>Another proposal, <a href="https://github.com/justinfagnani/proposal-mixins">maximally-minimal mixins</a>, covers some of the same needs. Unified proposal should emerge for stage 2.</p>
</section>
<section id="do-expressions">
<h2><code>do</code> expressions</h2>
<h4><a href="https://github.com/tc39/proposal-do-expressions">Spec</a></h4>
<div class="two-columns">
<div>
<pre><code class="language-js" data-trim data-keep-tags="u">
const x = do {
const tmp = f()
tmp * tmp + 1
}
</code></pre>
<p>Begone, nested ternaries!</p>
<pre><code class="language-js" data-trim data-keep-tags="u">
const x = do {
if (foo()) { f() }
else if (bar()) { g() }
else { h() }
}
</code></pre>
<p>Pretty cool for JSX too ➡️</p>
</div>
<div>
<pre><code class="language-jsx" data-trim data-keep-tags="u">
return (
<nav>
<Home />
{
do {
if (loggedIn) {
<LogoutButton />
} else {
<LoginButton />
}
}
}
</nav>
)
</code></pre>
</div>
</div>
<footer>Babel : <code>preset-stage-1</code>, <code>plugin-transform-do-expressions</code></footer>
</section>
<section id="pipeline">
<h2>Pipeline operator</h2>
<h4> (FP FTW #1) <a href="https://github.com/tc39/proposal-pipeline-operator">Spec</a></h4>
<p>Super-readable function composition. Inspired by similar features in OCaml, Elixir, Elm, F#…</p>
<p>Syntax is extremely in flux (<a href="https://github.com/tc39/proposal-pipeline-operator/wiki">4 competing proposals</a>).<br/>Here’s an example:</p>
<pre><code class="language-js" data-trim data-keep-tags="u">
// Old-school
const result = exclaim(capitalize(doubleSay('hello')))
// Hip
const result = 'hello'
<u>|></u> doubleSay
<u>|></u> capitalize
<u>|></u> exclaim
</code></pre>
</section>
<section id="partial-application">
<h2>Partial application</h2>
<h4>(FP FTW #2) <a href="https://github.com/tc39/proposal-partial-application">Spec</a></h4>
<p>Avoids hacky <code>bind(…)</code> usage. Can be done <em>ad hoc</em>, etc:</p>
<pre><code class="language-js" data-trim data-keep-tags="u">
const mul = (x, y) => x * y
const mul3 = mul(<u>?</u>, 3)
const fx = (prefix, seed, ...items)
const oneSeededFx = fx(<u>?</u>, 1, <u>...</u>)
</code></pre>
<p>Actually super advanced, <strong>lazy evals its binding context</strong> and arguments.
Also combines <strong>deliciously</strong> with pipelines:</p>
<pre><code class="language-js" data-trim data-keep-tags="u">
const newScore = player.score
|> add(7, ?)
|> clamp(0, 100, ?)
</code></pre>
</section>
<section id="function-binding">
<h2>Function binding</h2>
<h4>
(FP FTW #3)
<a href="https://github.com/tc39/proposal-bind-operator">Spec</a>
• Warning: STAGE ZERO!
</h4>
<p>Use context-based free functions with ad-hoc binding. Sort of an alternative to mixins.</p>
<pre><code class="language-js" data-trim data-keep-tags="u">
import { map, takeWhile, forEach } from 'iterlib'
getPlayers()
<u>::</u>map(x => x.character())
<u>::</u>takeWhile(x => x.strength > 100)
<u>::</u>forEach(x => console.log(x))
</code></pre>
<footer>Babel : <code>preset-stage-0</code>, <code>plugin-transform-function-bind</code></footer>
</section>
<section id="pattern-matching">
<h2>Pattern matching</h2>
<h4>
(FP FTW #4)
<a href="https://github.com/tc39/proposal-pattern-matching">Spec</a>
• Warning: STAGE ZERO!
</h4>
<p>Heavily inspired by Rust, F# and Haskell. Code branching based on structural argument matching.<br/>
Early syntax looks like this:</p>
<pre><code class="language-js" data-trim data-keep-tags="u">
const getLength = (vector) => <u>match (vector)</u> {
<u>{ x, y, z }:</u> Math.sqrt(x ** 2 + y ** 2 + z ** 2),
<u>{ x, y }:</u> Math.sqrt(x ** 2 + y ** 2),
<u>[...]:</u> vector.length,
<u>else:</u> {
throw new Error("Unknown vector type");
}
}
</code></pre>
</section>
</section> <!-- #esnext -->
<section>
<h1>Thank you!</h1>
<h3>And may JS be with you.</h3>
<br>
<p>Christophe Porteneuve</p>
<p><a href="https://twitter.com/porteneuve">@porteneuve</a></p>
<p class="breathing">
Slides are up at <a href="http://bit.ly/confoo-es2020">bit.ly/confoo-es2020</a><br/>
</p>
<p><small><a href="https://joind.in/talk/e8ec5">https://joind.in/talk/e8ec5</a></small></p>
</section>
</div>
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