Game of Performance
Alex Moldovan
@alexnmoldovan
Engineering Manager @ Fortech
Co-Founder @ Cluj JavaScripters
medium.com/@alexnm
"WHEN YOU PLAY THE
GAME OF PERFORMANCE
YOU WIN OR YOU DIE"
1.92s
3s - 7s
10s - 25s
420 Kb
httparchive.org
A brief history of web applications
( JavaScript vs Network )
1995
2008
2014
2018
Network
JavaScript
Ajax
SPA
SSR + SPA
SSR
UNIVERSAL APPS
Alice
game of performance
Browser
App Size
JavaScript
Alice
Round 1
VS
Browser
GET example.com
index.html
Time to first byte
Parse HTML
GET .css / .woff2
Dom Ready
Paint CSS
First meaningful paint
GET .js / .json
Page Interactive
Full Load
optimize critical path
SERVER RENDER YOUR APP
defer javascript Loading & execution
RENDER above the folD
High Priority
Low Priority
link preload
<link rel="preload" href="main.css" as="style">
<link rel="preload" href="webfont.woff2" as="font" type="font/woff2" crossorigin>
<link rel="preload" href="bg-image-narrow.png" as="image" media="(max-width: 600px)">
<link rel="preload" href="bg-image-wide.png" as="image" media="(min-width: 601px)">
Use HTTP/2
Alice
Round 2
VS
App Size
Size matters
minify + gzip
app.js
lib.js
minified
app.js
lib.js
minified + gzipped
679 kB
484 kB
137 kB
127 kB
app.css
156 kB
24 kB
app.css
Optimize imaGEs
1080px
360px
load images based on media queries
defer loading images below the fold
compress images (webp)
code spliting
app.bundle.js
300 kB
app.bundle.js
150 kB
account.bundle.js
100 kB
checkout.bundle.js
100 kB
import("../pages/myAccount")import("../pages/checkout")tree shaking
manage dependencies
MANAGE DEPENDENCIES
Careful with dependencies like moment.js and lodash
Invest time in your custom components if needed
Understand your browser usage, don't ship polyfills blindly
react-slick (12.2 kB) -> 3.41 kB
react-date-picker (25.4 kB) -> 3.22 kB
react-tooltip (9.7 kB) -> 1.42 kB
lightweight alternatives
Inferno
measure coverage
Alice
Round 3
VS
JavaScript
Write clean and efficient code
Limit dom interaction
jQuery
Angular.js
Backbone
React
Angular
Vue
Knockout
Vanilla *
pure components
View = F ( state )
avoid forced reflows
use profiling tools
passive event listeners
addEventListener('touchstart', onTouchStart, {passive: true});
Alice
bonus round
VS
Future
web app manifest
Alice
Service Workers
Web assembly
Tools
Lighthouse
Chrome dev tools
GTMetrix
calibre app
when do I have time?
Write Code
Write Tests
Performance
Security
The ladder of software quality
UX
Thank you! Questions?
Alex Moldovan
@alexnmoldovan
JavaScript Ninja @ Fortech
Co-Founder @ Cluj JavaScripters
medium.com/@alexnm