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
Practical Flow Type
Search
Sponsored
·
Ship Features Fearlessly
Turn features on and off without deploys. Used by thousands of Ruby developers.
→
yayoc
July 14, 2017
Programming
1
780
Practical Flow Type
Slides presented at gotanda.js
Nobuhide Yayoshi
yayoc
July 14, 2017
Tweet
Share
More Decks by yayoc
See All by yayoc
optional chainingの話
yayoc
0
280
Proxy's Black Magic
yayoc
0
190
What I did to improve performance score on Lighthouse
yayoc
2
2.7k
Other Decks in Programming
See All in Programming
CSC307 Lecture 02
javiergs
PRO
1
770
2026年 エンジニアリング自己学習法
yumechi
0
120
Patterns of Patterns
denyspoltorak
0
1.3k
GISエンジニアから見たLINKSデータ
nokonoko1203
0
190
[AI Engineering Summit Tokyo 2025] LLMは計画業務のゲームチェンジャーか? 最適化業務における活⽤の可能性と限界
terryu16
2
590
なぜSQLはAIぽく見えるのか/why does SQL look AI like
florets1
0
410
0→1 フロントエンド開発 Tips🚀 #レバテックMeetup
bengo4com
0
530
MDN Web Docs に日本語翻訳でコントリビュート
ohmori_yusuke
0
620
CSC307 Lecture 06
javiergs
PRO
0
670
QAフローを最適化し、品質水準を満たしながらリリースまでの期間を最短化する #RSGT2026
shibayu36
2
4.1k
CSC307 Lecture 07
javiergs
PRO
0
530
AtCoder Conference 2025
shindannin
0
1k
Featured
See All Featured
How to make the Groovebox
asonas
2
1.9k
Large-scale JavaScript Application Architecture
addyosmani
515
110k
Gemini Prompt Engineering: Practical Techniques for Tangible AI Outcomes
mfonobong
2
270
30 Presentation Tips
portentint
PRO
1
200
We Have a Design System, Now What?
morganepeng
54
8k
Balancing Empowerment & Direction
lara
5
860
For a Future-Friendly Web
brad_frost
182
10k
Visualization
eitanlees
150
17k
Kristin Tynski - Automating Marketing Tasks With AI
techseoconnect
PRO
0
130
B2B Lead Gen: Tactics, Traps & Triumph
marketingsoph
0
48
BBQ
matthewcrist
89
10k
Intergalactic Javascript Robots from Outer Space
tanoku
273
27k
Transcript
Practical FlowType @yayoc
Hello! I am Nobuhide Yayoshi 弥吉修英 You can find me
at @yayoc Frontend engineer, iOS At Fast Retailing
https://flow.org/
“ A static type checker for JavaScript Made By FB
Easy to adopt, easy to leave
Why Type Safety? ⊙ Efficient team development ⊙ Writing code
with confident ⊙ Documentable
Flow Type for Redux
Actions
Action Type with Union Type
Action Type Alias With Generics
Action Type Alias With Generics
$Exact
Without $Exact
Without $Exact
With $Exact
Reducer
Maybe, Optional
Refinements
$Exact Spread Object Issue! http://qiita.com/stomita/items/24a7d223acdc6a8715f4 https://github.com/facebook/flow/issues/2405
Flow Type for Class
Model Promise immutability
Model Promise immutability [flow] property `username` (user.js:20:7) Covariant property `username`
incompatible with contravariant use in assignment of property `username`
Model Promise immutability
Actions as Immutable
Flow Type for React Component
React PropTypes or Flow?
Components Prefer using Generic Style
Components Prefer using Generic Style
Components Prefer using Generic Style
React Component with $PropertyTypes
Adding Props With HOC
Adding Props With HOC
Adding Props With HOC
Error Case Adding Props With HOC
Other tips
https://github.com/flowtype/flow-typed flow-typed install Third Party https://github.com/facebook/immutable-js/blob/master/type -definitions/immutable.js.flow Finally, Immutable.js supports
Flow type in v4.0.0-rc1
Flow-coverage-report https://github.com/rpl/flow-coverage-report
Compare Typescript if you use Flow, you'll have much higher
type coverage much faster and you'll be able to sleep soundly. http://thejameskyle.com/adopting-flow-and-typescript.html
Swagger Flow Type A Swagger file has more than 8000
lines Writing Type Definitions manually is HARD
https://github.com/yayoc/swagger-to-flowtype https://github.com/yayoc/swagger-to-flowtype https://medium.com/@n_yayoshi/swagger-to-flowtype-generates-flow-type-aliases-8fab67776a4
None
swagger.yaml
flowtype.js
Conclusion ⊙ Utility types are useful ◦ $Exact ◦ $PropertyType
◦ Class ◦ Immutability ⊙ Prefer Flow than Proptypes ⊙ Prefer Generic Component ⊙ swagger-to-flowtype is useful
型安全 is Rock
We are hiring!!!
Thanks! Any questions? You can find me at @yayoc &
[email protected]
Credits Special thanks to all the people who made and
released these awesome resources for free: ⊙ Presentation template by SlidesCarnival ⊙ Photographs by Unsplash