Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
Re-evaluating Front-end Performance Best Practices
Search
benvinegar
April 21, 2015
Programming
15
1.6k
Re-evaluating Front-end Performance Best Practices
Fluent 2015
benvinegar
April 21, 2015
Tweet
Share
More Decks by benvinegar
See All by benvinegar
Getting the most out of JavaScript errors
benvinegar
1
300
JavaScript Error Reporting (and Why We Can't Have Nice Things)
benvinegar
0
210
FSTO: Re-evaluating Front-end Peformance Best Practices
benvinegar
9
890
Other Decks in Programming
See All in Programming
Progressive Web Apps for Rails developers
siaw23
2
530
VS Code extension: ドラッグ&ドロップでファイルを並び替える
ttrace
0
160
Micro Frontends for Java Microservices - dev2next 2024
mraible
PRO
0
190
Frontend Magic mit CSS Houdini
joergneumann
0
420
Go製CLIツールGatling Commanderによる負荷試験実施の自動化
okmtz
3
650
The Myth of the Modular Monolith - Day 2 Keynote - Rails World 2024
eileencodes
6
230
タイミーにおけるデータの利用シーンと データ基盤の挑戦
marufeuille
4
3.1k
App Router 悲喜交々
quramy
7
370
Subclassing, Composition, Python, and You
hynek
3
110
為醫療加裝Python的引擎
cclai999
0
270
利用者視点で考える、イテレータとの上手な付き合い方
syumai
4
210
ポケモンで考えるコミュニケーション / Communication Lessons from Pokémon
mackey0225
4
140
Featured
See All Featured
Design and Strategy: How to Deal with People Who Don’t "Get" Design
morganepeng
125
18k
Atom: Resistance is Futile
akmur
261
25k
4 Signs Your Business is Dying
shpigford
180
21k
Web development in the modern age
philhawksworth
205
10k
Making the Leap to Tech Lead
cromwellryan
130
8.8k
Being A Developer After 40
akosma
84
590k
Bootstrapping a Software Product
garrettdimon
PRO
304
110k
10 Git Anti Patterns You Should be Aware of
lemiorhan
653
59k
We Have a Design System, Now What?
morganepeng
49
7.1k
Automating Front-end Workflow
addyosmani
1365
200k
Practical Orchestrator
shlominoach
185
10k
GraphQLとの向き合い方2022年版
quramy
43
13k
Transcript
re-evaluating front-end performance best practices
@bentlegen
None
None
car·go cult
cargo cult web performance
how does it happen?
deprecated … • books • blog posts • best practice
guides • StackOverflow answers • performance analysis tools • practices on live websites • conference talks like this one
the agenda • hostname sharding • for-loop array length caching
• dynamic script insertion
hostname sharding
in the beginning (HTTP 1.0)
with more connections 2 4 8 www www www
with hostname sharding 2 2 2 www www1, www2 www1
www2 www3 www4
still common Website # Static Hosts plus.google.com 4 tumblr.com 4
alibaba.com 4 theverge.com 4 ebay.com 6 businessinsider.com 6 netflix.com 11!
None
not a big deal anymore
browser connections/origin Browser # HTTP / origin Chrome 42 6
Firefox 37 8 Safari 7 6 IE 8, 9 6 IE 10 8 IE 11 13 bit.ly/rprf-bscope
chrome caps parallel image requests at 10 anyways bit.ly/rprf-bscope
rise of https stalled/ proxy negotiation dns! lookup connection +
tls/ssl time-to- first-byte download tls/ssl handshake
and http/2 will make all this irrelevant anyways
“2 domains for non-SPDY modern browsers” – Souders in 2013
bit.ly/rprf-2domains
etsy case study • 4 image domains → 2 •
50-80 ms faster for image heavy pages • 30-50 ms faster overall • up to 500ms faster on mobile bit.ly/rprf-etsy
the web’s moving on Website # Static Hosts netflix.com* 1
nytimes.com 1 youtube.com 2 twitter.com 2 facebook.com 2 pinterest.com 2 bbc.co.uk 2 etsy.com 3
looping
specifically array length caching in for loops
for (var i = 0, len = arr.length; i <
len; i++) { // do stuff } for (var i = 0; i < arr.length; i++) { // do stuff } vs
None
None
None
does it still hold?
cache vs no cache Chrome 42 Firefox 37 Safari 7
IE9+ IE8 ops/second (normalized), bigger is better cache no cache 78%
V8 (and other browsers) recognize this pattern bit.ly/rprf-v8opt
uncached version
cached version
“we should start assuming that our code is optimized” -
Vyacheslav Egorov, V8 bit.ly/rprf-v8opt
if you can trivially optimize it, the browser (probably) can
too
mobile disagrees, a little Chrome 41 (Android 5.1) Firefox 34
(Android 5.1) Safari (iOS 8) ops / second (normalized), bigger is better cache no cache 95%
if you think you’re going to get performance gains from
optimizing for loops you’re gonna have a bad time
dynamic script insertion
<script> var script = document.createElement('script'); script.src = '/app.js'; document.getElementsByTagName('head')[0] .appendChild(script);
</script> vs <script src="/app.js"></script>
None
None
who does this? • analytics: GA, Mixpanel, Chartbeat, Wordpress •
widgets: Disqus, Facebook Comments • JS module loaders: RequireJS, LabJS • script managers: Google Tag Manager, Segment
small problem: CSS Object Model
CSS Object Model (CCSOM) <link type="text/stylesheet" href="/main.css"/> ! ! !
<script> window.getComputedStyle(document.body).margin; </script> can’t execute until CSS ready
CSSOM + dynamic script insertion <link type="text/stylesheet" href="/main.css"/> ! !
! <script> var script = document.createElement('script'); script.src = '/app.js'; document.getElementsByTagName('head')[0] .appendChild(script); </script> can’t execute until CSS ready
dynamic script insertion scripts execute inline scripts can’t execute until
CSSOM ready; downloading is delayed
blocking 2nd script downloads after 1st executes 1st script preloaded
1st script executes
“Have we been doing it all wrong?” - Ilya Grigorik,
2014 bit.ly/rprf-injected
3rd option: async attribute <script async src="/app.js"></script>
ideal: async attribute both scripts execute all 3 resources download
in parallel
we should probably start using async
None
closing thoughts
don’t always believe what you read on the internet
benchmark your own stuff
benchmark your own stuff every year, apparently
always bet on browsers (and JS engines)
thanks
acknowledgements • performance research: Steve Souders, Ilya Grigorik, Guy Podjarny,
Vyacheslav Egorov, Jonathan Klein, Paul Irish, Nicholas Zakas • photos: Christian Junker, André Hofmeister, “My aim is true” • me: Ben Vinegar (@bentlegen) • office hours @ 1:30 PM today