The Hitchhiker's Guide to the Front-End Performance, 2019 edition

The Hitchhiker's Guide to the Front-End Performance The Hitchhiker's Guide
to the Front-End Performance 2019 EDITION

˜ I’m from… ˜

What do we know about perf? What do we know
about perf?

˜ GZIP everything ˜ Minify both CSS and JS ˜
HTML must be compressed ˜ CSS goes on <head> ˜ JS goes lastly on </body> ˜ Optimize all the images (e.g. svgo)

Issues I was facing Issues I was facing

˜ What I do at …

˜ JavaScript ˜

"Write modern, idiomatic JavaScript, and let the JavaScript engine worry
about making it fast." - Mathias Bynens, BrazilJS 2018

˜ JavaScript ˜

Before version 5.9 of V8 came out, the engine used
two compilers: ˜ Full Codegen A simple and very fast compiler that produced simple and relatively slow machine code ˜ Crankshaft A more complex (Just-In-Time) optimizing compiler that produced highly-optimized code

Optimization Killers

Optimization Killers ~ Generators and async functions ~ for-of and
destructuring ~ try-catch and try-finally ~ Compound let or const assignment ~ Object literals that contain __proto__, or get or set declarations. ~ debugger or with statements ~ Literal calls to eval() ~ …

Performance cliffs in Crankshaft (function good() {  const start =
Date.now();  for (var i = 0; i < 1e8; i++) {}  console.log(Date.now() - start);  })(); ˜80ms (function bad() {  const start = Date.now();  for (var i = 0; i < 1e8; i++) {}  console.log(Date.now() - start);  const whatever = 1;  })(); ˜230ms

Performance cliffs in Crankshaft (function good() {  const start =
Date.now();  for (var i = 0; i < 1e8; i++) {}  console.log(Date.now() - start);  })(); (function bad() {  const start = Date.now();  for (var i = 0; i < 1e8; i++) {}  console.log(Date.now() - start);  const whatever = 1;  })(); ˜3x slowdown with Crankshaft

The new execution pipeline is built on top of Ignition,
V8’s interpreter, and TurboFan, V8’s newest optimizing compiler.

Optimization Killers ~ Generators and async functions ~ for-of and
destructuring ~ try-catch and try-finally ~ Compound let or const assignment ~ Object literals that contain __proto__, or get or set declarations. ~ debugger or with statements ~ Literal calls to eval() ~ …

60% faster web developer tools http://v8project.blogspot.com/2017/11/web-tooling-benchmark.html

https://twitter.com/popeindustries/status/895575424406867968

"Write modern, idiomatic JavaScript, and let the JavaScript engine worry
about making it fast." - Mathias Bynens, BrazilJS 2018

˜ fixing perf issues be like ˜

˜ Problems ˜

˜ #1 ˜ Critical Resources Late Delivered

˜ Connecting to critical origins (preconnect) ˜ Asset for current
page (preload) ˜ Asset for future navigation (prefetch)

˜ What it does… Preconnect allows the browser to setup
early connections before an HTTP request is actually sent to the server. This includes: ˜ DNS lookups ˜ TLS negotiations ˜ TCP handshakes This in turn: ✔ Eliminates roundtrip latency ✔ Saves time for users

˜ Bring me the ! 100MS 200MS 300MS 400MS 500MS
600MS 700MS HTML CSS FONT 1 FONT 2 Fonts start loading Fonts rendered

˜ Bring me the ! 100MS 200MS 300MS 400MS 500MS
600MS 700MS HTML CSS FONT 1 FONT 2 Fonts start loading Fonts rendered FONT 1 FONT 2

˜ What it does… Some of the benefits of the
preload directive include: ✔ Gives the browser the ability to determine the resource type (it can tell if the same resource can be reused in the future) ✔ The browser can determine if the request is compliant with the content security policy ✔ The browser can send the appropriate accept headers based on resource type

˜ What it does… ✔ Fetch resources in the background
(idle time) ✔ Store them in the browser’s cache It can be:

Link Prefetching DNS Prefetching Prerendering

Link Prefetching DNS Prefetching Prerendering ˜ What it does… Allows
the browser to fetch resources, store them in cache, assuming that the user will request them. <link rel="prefetch" href="/uploads/images/pic.png"> ˜ What can $% do…

the browser to perform DNS lookups on a page in the background while the user is browsing. <link rel=“dns-prefetch” href="#$fonts.googleapis.com"> ˜ What can $% do…

the browser to render the entire page in the background, all the assets of a document. <link rel=“prerender” href=“https://xandaviao.com.br/”> ˜ What can $% do…

the browser to render the entire page in the background, all the assets of a document. <link rel=“prerender” href=“https://xandaviao.com.br/”> ˜ What can $% do… ⚠ ❌ ❌ ⚠

the browser to render the entire page in the background, all the assets of a document. <link rel=“prerender” href=“https://xandaviao.com.br/”> ˜ What can $% do… ✘ You want to be more careful with prerendering as it is resource heavy and can cause bandwidth waste, especially on mobile devices

https://wicg.github.io/priority-hints/

%%%& A script is to be loaded with critical importance
as it is necessary for the core user experience ''( <script src=foo importance=critical> %%%& An image is to be loaded with high importance. It could be important but not critical to the overall experience loading up. ''( <img src=foo importance=high> %%%& It can be used to indicate low importance/non-blocking style which isn't impacting the core experience. ''( <link rel=stylesheet href=foo importance=low>

#$ First import(/* webpackPrefetch: 3 */ "assets/images/foo.jpg"); #$ Second import(/*
webpackPrefetch: 2 */ "modules/foo"); #$ Last import(/* webpackPrefetch: 1 */ “modules/bar");

Preloaded Chunk Prefetched Chunk X

Preloaded Chunk Prefetched Chunk X ˜ Starts loading in parallel
to the parent chunk ˜ Focuses on current navigation ˜ Fetches resources with high-priority ˜ Is instantly downloaded ˜ Starts after the parent chunk finish ˜ Focuses on fetching resources for the next navigation ˜ Fetches resources with low priority ˜ Is downloaded in browser idle time

˜ #2 ˜ Blocked First Paint

˜ Avoid invisible text while web fonts are loading ˜
Reduce render blocking scripts and stylesheets ˜ Server-side render stuff

˜ What says… ˜ What can $% do… @font-face {
font-family: "Open Sans Regular"; src: url(“./OpenSans-Regular-BasicLatin.woff2") format("woff2"); font-display: swap; }

˜ What says… ˜ What can $% do… @font-face {
font-family: "Open Sans Regular"; src: url(“./OpenSans-Regular-BasicLatin.woff2") format("woff2"); font-display: swap; } ˜ What it does… The initial font displayed is the first system font in the stack. When the custom font has loaded, it will kick in and replace the system font that was initially displayed.

˜ What says… ˜ What can $% do… https://github.com/addyosmani/critical

https://rauchg.com/2014/7-principles-of-rich-web-applications

https://nextjs.org

˜ #3 ˜ Bloated Pages

˜ Audit your assets regularly ˜ Code Split (Routes, Components,
Vendor bundles) + Dynamic Import stuff ˜ Remove unused library code + Tree Shake

Bundlephobia Import Cost for VSCode Webpack Bundle Analyzer

1.8s bootup 0.78s bootup ˜ What says… ˜ What can
$% do…

1.8s bootup 0.78s bootup ˜ What says… ˜ What can
$% do… 56% faster

https://github.com/GoogleChromeLabs/webpack-libs-optimizations

˜ #4 ˜ Unnecessary Resources

˜ Compress (gzip, brotli)

˜ -30%

⚠ ❌ ❌ ⚠

˜ Compress (gzip, brotli)

˜ #5 ˜ Unused Code

˜ Code coverage in DevTools (Page load, runtime) ˜ Lighthouse
Coverage Audit ˜ Remove unused code to improve load time ˜ Write regression tests

95% unused

https://github.com/purifycss/purifycss

(+ jest-image-snapshot)

˜ #6 ˜ Unoptimized Images

˜ Optimize images ˜ Use lighter formats ˜ Use responsive
images

˜ What says…

˜ GUI ˜ ImageOptmin (Mac) XNConvert (Cross-platform) ˜ Build ˜
imagemin libvips ˜ CDN ˜ Cloudinary Imgix Fastly Akamai ˜ CDN ˜ (self-hosted) Thumbor ImageFlow ˜ What can $% do…

˜ GUI ˜ ImageOptmin (Mac) XNConvert (Cross-platform) ˜ Build ˜
imagemin libvips ˜ CDN ˜ Cloudinary Imgix Fastly Akamai ˜ CDN ˜ (self-hosted) Thumbor ImageFlow

˜ What it does…

images

<img src="banda_magnificos.gif"> 7.3mb <video autoplay muted playinline> <source src="banda_magnificos.mp4" type="video/mp4">
</video> 1.3MB <video autoplay muted playinline> <source src=“banda_magnificos.webm” type=“video/webm"> </video> 960kb 80%+ savings

images

https://developer.mozilla.org/en-US/docs/Web/API/NetworkInformation/effectiveType

4G+ (Video) ˜1mb 2G-3G (Static Image) ˜30kb

images

˜ #7 ˜ Wasted Renders

Virtualizing a list of items involves maintaining a window and
moving that window around your list. "How does windowing work?" by Brian Vaughn

https://github.com/bvaughn/react-virtualized

10K items wo/ virtualization 10K items w/ virtualization X

w/ virtualization X wo/ virtualization "Rendering large lists with react-window"
by Addy Osmani

w/ virtualization X wo/ virtualization ˜242.7ms ˜2.4ms "Rendering large lists
with react-window" by Addy Osmani

˜ Use referentially equal stuff ˜ Use PureComponent/memo (when it
makes sense) ˜ (In the future) Take benefit from time slicing ˜ Take benefit from techniques like windowing

"In God we trust; all others must bring data." -
W. Edwards Deming

˜ Senior Software Engineer, Front- End @beakyn ˜ @ythecombinator on
the webs ˜ addicted to emojis, memes and beer

https://speakerdeck.com/ ythecombinator/the-hitchhiker-s-guide-to-the-front-end-performance-2019-edition

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The Hitchhiker's Guide to the Front-End Performance, 2019 edition

The Hitchhiker's Guide to the Front-End Performance, 2019 edition

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