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
You don't know Promises - IT Konekt April 2019
Search
Ivan Jovanovic
April 20, 2019
Technology
1
45
You don't know Promises - IT Konekt April 2019
Ivan Jovanovic
April 20, 2019
Tweet
Share
More Decks by Ivan Jovanovic
See All by Ivan Jovanovic
Micro Frontends - A microservice approach to the modern web - Oredev 2019
ivanjov
0
68
Micro Frontends - A microservice approach to the modern web - O'Reilly Software Architecture Berlin 2019
ivanjov
0
55
React State - The Good, the Bad and the Ugly - ArmadaJS
ivanjov
0
88
Thinking Reactive in JavaScript - Sphere.it JS Krakow
ivanjov
0
48
Micro Frontends - A microservice approach to the modern web - PHPSrbija
ivanjov
0
200
Micro Frontends - A microservice approach to the modern web - Codemotion Rome 2019
ivanjov
0
320
Mikro Frontendi - Uvod - Novi Sad JS
ivanjov
0
130
Software engineer marketing done right – career tips from my experience.
ivanjov
0
27
Micro Frontends - A microservice approach to the modern web - Full Stack London 2018
ivanjov
0
170
Other Decks in Technology
See All in Technology
Segment Anything Model 2
tenten0727
3
710
Envoy External AuthZとgRPC Extensionを利用した「頑張らない」Microservices認証認可基盤
andoshin11
0
260
watsonx.ai Dojo 環境準備について
oniak3ibm
PRO
0
340
JTCや セキュリティチェックリストが夢の跡
nikinusu
1
720
ついに出た!OpenAIの最新モデル「o1」って何がすごいの?
minorun365
PRO
3
1.2k
Oracle Autonomous Database:サービス概要のご紹介
oracle4engineer
PRO
1
7.1k
LLVM/ASMを使った有限体の高速実装
herumi
0
120
OR学会2024秋_短期収益と将来のオフ方策評価性能を考慮したクーポン割当方策混合比の決定
recruitengineers
PRO
4
470
Mocking in Rust Applications
taiki45
2
410
AI活用したくてもできなかった不動産SaaSの今とこれから
nealle
0
340
言葉は感情の近似値である。その感情と言葉の誤差を最小化しよう ~コミュニケーションにおけるアナログ/デジタル変換の課題に立ち向かう~
nktamago
0
230
DevRelの始め方
moongift
PRO
2
390
Featured
See All Featured
Building Adaptive Systems
keathley
36
2.1k
ParisWeb 2013: Learning to Love: Crash Course in Emotional UX Design
dotmariusz
109
6.9k
Practical Orchestrator
shlominoach
185
10k
Designing with Data
zakiwarfel
98
5k
How STYLIGHT went responsive
nonsquared
93
5.1k
For a Future-Friendly Web
brad_frost
174
9.3k
The Straight Up "How To Draw Better" Workshop
denniskardys
230
130k
Designing Dashboards & Data Visualisations in Web Apps
destraynor
227
52k
Pencils Down: Stop Designing & Start Developing
hursman
119
11k
The Psychology of Web Performance [Beyond Tellerrand 2023]
tammyeverts
36
2.1k
CoffeeScript is Beautiful & I Never Want to Write Plain JavaScript Again
sstephenson
158
15k
We Have a Design System, Now What?
morganepeng
48
7.1k
Transcript
You don't know Promises
I am Ivan Jovanovic Senior Software Engineer, Tech Speaker You
can find me at @ivanjov96 or https://ivanjov.com Hello! IJ Consulting
Why I don't know Promises?
None
None
I am here today To show you how Promises really
work!
JavaScript is strange because ‒ It was built for 10
days ‒ It has one thread ‒ It is synchronous and asynchronous ‒ It is everywhere ‒ It is different
Only one thread And the event loop
None
How do we handle async code? Promises Callbacks Async/await
Callbacks Where everything began... 1
“ A callback is a function that is passed as
an argument and will be executed after another function has finished executing.
None
None
Promises Changed everything 2
“ The Promise object represents the eventual completion (or failure)
of an asynchronous operation, and its resulting value.
None
None
How Promises really work? The answer is a Microtask queue!
None
Microtask queue ‒ Independent queue ‒ Used by: process.nextTick, Promises,
Object.observe, MutationObserver ‒ Faster than the main queue and may be drained several times in a single event loop tick
None
Next TICK ONE Next TICK TWO TIMEOUT AFTER-ONE TIMEOUT AFTER-TWO
Promise methods ‒ Promise.all(iterable) ‒ Promise.race(iterable) ‒ Promise.resolve(value) ‒ Promise.reject(reason)
Promise.all(iterable)
Rejected situation
Promise.race(iterable)
Promisify non-Promise code
Native Promises from libraries
Async/await Comes to the rescue 3
“ Async/Await is a special syntax for working with Promises.
None
Most common problems with Promises that we see every day!
9
Nested promises 1
None
None
Broken Promise chain 2
None
None
Mixing sync and async code 3
None
None
None
Missing catch 4
None
None
None
Forget to return a Promise 5
None
None
Promisified synchronous code 6
None
Mixing Promise and Async/Await 7
None
None
Async function that returns Promise 8
None
None
None
Define a callback as an async function 9
None
Clinic.js https://clinicjs.org/
Conclusion ‒ JS is crazy and great at the same
time! ‒ Async behavior is a pro, not a con. ‒ Be careful when using Promises, it's great and dangerous at the same time!
Any questions ? You can find me at ‒ @ivanjov96
‒
[email protected]
Thanks!