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
Modern TypeScript
Search
Taketoshi Aono(青野健利 a.k.a brn)
March 23, 2020
Programming
2
820
Modern TypeScript
Modern TypeScript coding techniques and tips.
Taketoshi Aono(青野健利 a.k.a brn)
March 23, 2020
Tweet
Share
More Decks by Taketoshi Aono(青野健利 a.k.a brn)
See All by Taketoshi Aono(青野健利 a.k.a brn)
document.write再考
brn
6
3k
Parsing Javascript
brn
14
9.3k
JSON & Object Tips
brn
1
500
CA 1Day Youth Bootcamp for Frontend LT
brn
0
960
javascript - behind the scene
brn
3
750
tc39 proposals
brn
0
880
プロダクト開発とTypeScript
brn
8
2.9k
React-Springでリッチなアニメーション
brn
1
700
javascript internationalization API
brn
0
900
Other Decks in Programming
See All in Programming
Google I/O Extended Incheon 2025 ~ What's new in Android development tools
pluu
1
250
CEDEC 2025 『ゲームにおけるリアルタイム通信への QUIC導入事例の紹介』
segadevtech
3
820
20250808_AIAgent勉強会_ClaudeCodeデータ分析の実運用〜競馬を題材に回収率100%の先を目指すメソッドとは〜
kkakeru
0
130
No Install CMS戦略 〜 5年先を見据えたフロントエンド開発を考える / no_install_cms
rdlabo
0
480
Jakarta EE Meets AI
ivargrimstad
0
650
Webinar: AI-Powered Development: Transformiere deinen Workflow mit Coding Tools und MCP Servern
danielsogl
0
110
なぜあなたのオブザーバビリティ導入は頓挫するのか
ryota_hnk
5
580
プロダクトという一杯を作る - プロダクトチームが味の責任を持つまでの煮込み奮闘記
hiliteeternal
0
450
抽象化という思考のツール - 理解と活用 - / Abstraction-as-a-Tool-for-Thinking
shin1x1
1
950
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
330
あなたとJIT, 今すぐアセンブ ル
sisshiki1969
1
590
#QiitaBash TDDで(自分の)開発がどう変わったか
ryosukedtomita
1
360
Featured
See All Featured
A better future with KSS
kneath
239
17k
個人開発の失敗を避けるイケてる考え方 / tips for indie hackers
panda_program
110
19k
Why You Should Never Use an ORM
jnunemaker
PRO
58
9.5k
GitHub's CSS Performance
jonrohan
1031
460k
Building a Modern Day E-commerce SEO Strategy
aleyda
43
7.4k
A designer walks into a library…
pauljervisheath
207
24k
Creating an realtime collaboration tool: Agile Flush - .NET Oxford
marcduiker
31
2.2k
Measuring & Analyzing Core Web Vitals
bluesmoon
8
550
The World Runs on Bad Software
bkeepers
PRO
70
11k
Scaling GitHub
holman
461
140k
"I'm Feeling Lucky" - Building Great Search Experiences for Today's Users (#IAC19)
danielanewman
229
22k
The Art of Programming - Codeland 2020
erikaheidi
54
13k
Transcript
Modern TypeScript
Name !CSO 5BLFUPTIJ"POP੨݈ར Occupation 'SPOUFOE%FWFMPQFS1SPEVDU0XOFS Company $ZCFSBHFOU"EUFDI4UVEJP"*.FTTFOHFS OSS $POUSJCVUPSPG7
About IUUQJOGPCODI
ຊͷ༰ ࠷ۙͷTypeScript৽ػೳ Tips
Null Coalescing
value ?? orValue
// ҎԼͷܗࣜͩͱ0ۭจࣈʹҾ͔͔ͬΔ value || orValue value? value: orValue // Null
CoalescingҎԼͷܗࣜͱಉ͡ޮՌ value != null? value: orValue
Null Coalescing ͕null/undefinedͷ߹ʹ??Ҏ߱Λ࣮ߦ͢Δ ཧORͷԋࢉࢠࠓޙ΄ͱΜͲ͏ඞཁͳ͍ ·ͨɺࠓ·ͰifจதͰऑ͍ൺֱΛ͍ͬͯͨՕॴɺlintΛ੍ͤͣʹࡁ ΉΑ͏ʹॻ͖͑ΒΕΔ
// ࠓ·Ͱͷnull/undefinedͷνΣοΫํ๏ if (value != null) { } // ࠓޙlintʹ==ΛౖΒΕΔࣄͳ͘??Ͱஔ͖͑ΒΕΔ
if (value ?? null) { }
Optional Chaining
foo?.bar?.baz?.qux
Optional Chaining ΦϒδΣΫτ͕null/undefinedͩͬͨ߹ʹϓϩύςΟΞΫηεΛ࣮ ߦͤͣundefinedΛฦ͢ ͕ଘࡏ͢Δͱ͖͚ͩϓϩύςΟΞΫηεΛߦ͏ ࠓ·ͰࣗલͰMaybe/OptionalΫϥεΛ࣮͍ͯͨ͠έʔεΛஔ͖͑Β ΕΔ
// Null CoalescingͱΈ߹ΘͤΔͱڧྗ return foo?.bar?.baz?.qux ?? value; // ؔݺͼग़͕͠ඞཁ const
x = (...args: any): any => {} (foo?.bar?.baz ?? x)()
Top Level Await
await foo();
Top Level Await ࠓ·ͰawaitasyncؔͰͷΈॻ͚͕ͨɺ3.8ΑΓτοϓϨϕϧͰ هड़Ͱ͖ΔΑ͏ʹͳͬͨ
Recursive Type Alias
type ReadonlyDeep<T> = { [P in keyof T]: ReadonlyDeep<T[P]> }
Recursive Type Alias ࠶ؼతͳܕΛ୯७ͳType AliasͰදݱͰ͖ΔΑ͏ʹͳͬͨ Ҏલinterfaceͷextends͕ඞཁͩͬͨ
Tips
const assertion
const value = 'value' as const // value: 'value'
Const assertion ͷ͋ͱʹas constͱ͚ͭΔ͜ͱͰ string/number/boolean/array/object ΛϦςϥϧλΠϓͱͯ͠ఆٛ͢Δ͜ͱ͕Ͱ͖Δ ※ϦςϥϧλΠϓͱ͕ͦͷ··ܕͱͯ͠ѻΘΕΔͷ ͦͷͨΊɺReduxͷܕఆٛΛconst assertionΛͬͯ ΑΓγϯϓϧʹఆٛ͢Δ͜ͱ͕Ͱ͖Δ
const fooAction = (payload: {value: string}) => { return {
type: "FOO" as const, payload } } const barAction = (payload: {value: string}) => { return { type: "BAR" as const, payload } } type ActionTypes = ReturnType<typeof fooAction> | ReturnType<typeof barAction>; // "FOO" | "BAR" const reducer = (state: State, action: ActionTypes) => { switch (action.type) { case "BAZ": // Error '"BAZ"' is not comparable to type '"FOO" | "BAR"' ... } }
String literal type
String literal type ݸਓతʹจࣈྻશͯenum͔ΦϒδΣΫτʹೖΕ͍͕ͯͨɺ TypeScriptશͯstring literal typeͱͯ͠ܕఆٛͯ͠ɺϦς ϥϧϕλॻ͖͕Ұ൪γϯϓϧͳͷͰͳ͍͔ͱߟ͑ΔΑ͏ʹͳͬͨ
const foo = (type: 'foo' | 'bar' | 'baz' |
'qux') => { ... } foo('foo'); foo('bar');
String literal type Θ͔Γ͘͢γϯϓϧͳͷͰɺจࣈྻenumશͯจࣈྻܕʹ͢Δͷ͕͓͢ ͢Ί จࣈྻఆͪΌΜͱมʹೖΕ·͠ΐ͏
͝ਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠