TypeScript
Beyond the basics 🚀
Overview
- What is the talk about? 🤔
- My origin story 🦸♂️
- What do you know now? 🙋♂️
- What will you know at the end? 💡
Overview
- What is the talk about? 🤔
-
- Showcasing lesser known features
- Advanced TypeScript concepts
- My origin story 🦸♂️
- What do you know now? 🙋♂️
- What will you know at the end? 💡
Overview
- What is the talk about? 🤔
- My origin story 🦸♂️
-
- Why am I giving this presentation?
- What do you know now? 🙋♂️
- What will you know at the end? 💡
Overview
- What is the talk about? 🤔
- My origin story 🦸♂️
- What do you know now? 🙋♂️
-
- Superset of JavaScript
- Static type analysis
- Extends JavaScript with new features
- What will you know at the end? 💡
Overview
- What is the talk about? 🤔
- My origin story 🦸♂️
- What do you know now? 🙋♂️
- What will you know at the end? 💡
-
- One or two new features/tricks
- When/why to use them
- Whether you just wasted 20 minutes 😉
Declaration Merging
Declaration
"A statement which introduces a name into the program"
Chat GPT 2024
🙋♂️
Branded Types
No!
(And TypeScript didn't catch our mistake 😢)What is a branded type?
What is a branded type?
Success! 🥳
🙋♂️
any, unknown and never
Foundational Concepts
- Narrow and wide types
- Type compatibility
Narrow vs. wide wypes
Narrow vs. wide wypes
Narrow vs. wide wypes
Narrow vs. wide wypes
-
Any & Unknown
- Widest possible type
- Anything can be assigned to them
-
Never
- Narrowest possible type
- Nothing can be assigned to it
Type compatibility
When to use "any"?
- ✅ Non-production code (e.g. prototype or PoC)
- ✅ Within a well defined boundary
- ✅ When type safety is difficult or impossible
- ❌ When you don't know the type
- ❌ As a function parameter or return
Consider other options
Consider other options
When to use "unknown"?
- ✅ When you don't know the type
- ✅ As a function parameter or return
When to use "unknown"?
When to use "unknown"?
When to use "unknown"?
TLDR;
Use "unknown" any time you would use "any" - unless you have a good reason not to.When to use "never"?
- ✅ Complex generics
- ✅ Exhaustivness checking
- ✅ Functions that don't return
When to use "never"?
When to use "never"?
When to use "never"?
When to use "never"?
When to use "never"?
🙋♂️
Conclusion
- Declaration Merging
- Branded Types
- Any, Unknown and Never
Thank You! ❤️
Further Reading
- Articles
- Tools
