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
340
JavaScript Error Reporting (and Why We Can't Have Nice Things)
benvinegar
0
220
FSTO: Re-evaluating Front-end Peformance Best Practices
benvinegar
9
1k
Other Decks in Programming
See All in Programming
サーバーサイドのビルド時間87倍高速化
plaidtech
PRO
0
490
Langfuseと歩む生成AI活用推進
licux
3
300
MCPで実現するAIエージェント駆動のNext.jsアプリデバッグ手法
nyatinte
6
880
RDoc meets YARD
okuramasafumi
1
120
コーディングは技術者(エンジニア)の嗜みでして / Learning the System Development Mindset from Rock Lady
mackey0225
2
580
Portapad紹介プレゼンテーション
gotoumakakeru
1
130
Oracle Database Technology Night 92 Database Connection control FAN-AC
oracle4engineer
PRO
1
210
Kiroの仕様駆動開発から見えてきたAIコーディングとの正しい付き合い方
clshinji
1
150
Microsoft Orleans, Daprのアクターモデルを使い効率的に開発、デプロイを行うためのSekibanの試行錯誤 / Sekiban: Exploring Efficient Development and Deployment with Microsoft Orleans and Dapr Actor Models
tomohisa
0
210
AHC051解法紹介
eijirou
0
620
TDD 実践ミニトーク
contour_gara
0
150
『リコリス・リコイル』に学ぶ!! 〜キャリア戦略における計画的偶発性理論と変わる勇気の重要性〜
wanko_it
1
600
Featured
See All Featured
Scaling GitHub
holman
462
140k
GraphQLの誤解/rethinking-graphql
sonatard
71
11k
Building Flexible Design Systems
yeseniaperezcruz
328
39k
Why You Should Never Use an ORM
jnunemaker
PRO
59
9.5k
How STYLIGHT went responsive
nonsquared
100
5.7k
GraphQLとの向き合い方2022年版
quramy
49
14k
Git: the NoSQL Database
bkeepers
PRO
431
65k
Art, The Web, and Tiny UX
lynnandtonic
302
21k
Being A Developer After 40
akosma
90
590k
Optimizing for Happiness
mojombo
379
70k
The Psychology of Web Performance [Beyond Tellerrand 2023]
tammyeverts
49
3k
Done Done
chrislema
185
16k
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