TypeScript Fundamentals — Getting a Bit Deeper
Syntax - Tasty Web Development Treats
Mastering Type Assertions in TypeScript
This chapter explores type assertions in TypeScript, clarifying the difference from typecasting and emphasizing compile-time implications. It discusses practical applications in web development, particularly in React, while highlighting the importance of type safety and the use of JS doc comments for enhanced coding practices.
In this episode of Syntax, Scott and Wes continue their discussion of TypeScript Fundamentals with a deeper diver into more advanced use cases.
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Show Notes Deep end stuff03:30 - any vs unknown
06:20 - never
- https://twitter.com/Igorbdsq/status/1351681019196436482 09:14 - .d.ts
- Definition files
- Usually for existing libraries that don’t have types
- Can be generated or hand-written
- Also really handy for pure JS projects, you still get good autocomplete because of these
13:25 - Type generation
- Can be generated from GraphQL, or Schemas, or from JSON Output
17:20 - TypeScript generics (variables)
- Kind of like functions, they return something different based on what you pass it
- makeFood
- makeFood
- This function makes food and shares lots of the same functionality between making a pizza and sandwich
- If the only thing that differs is the type returned, we can use generics
- You often see this as a single char T
- It can be anything
- Promise is a generic
- querySelector uses generics
21:48 - Promises / Async + Await
- Functions now return a Promise type, but with a generic
- Promise
- Promise
- Promise, Request, Request
- stringified
- added headers
29:48 - Type assertion (type casting)
- Type assertion is when you want to tell TypeScript “Hey I know better than you”.
- Two ways:
- as keyword (most popular)
- someValue as HTMLParagraphElement
- Tagged before
- someValue
- as keyword (most popular)
34:14 - TypeScript without TypeScript (JSDoc / TSDoc)
- Really nice!
- You can also add comments / descriptions
- https://github.com/developit/redaxios/blob/master/src/index.js
40:08 - Interfaces vs Types
- Interfaces have better perf
- https://twitter.com/wesbos/status/1362418379919937545
- https://blog.logrocket.com/types-vs-interfaces-in-typescript/
- What do you default to?
44:27 - Interface or Types
- Scott - Types
- Wes - Interfaces
44:50 - any vs unknown
- Scott - any
- Wes - unknown / any
46:52 - Any (No Implicit or Implicit Allowed)
- Scott - No implicit any
- Wes - No implicit any
48:31 - Return types (Implicit or Explicit)
- Scott - Explicit always
- Wes - Not always
50:49 - Compile (TSC, Strip TS)
- Scott - Strip
- Wes - Both
52:38 - Type Assertion (as or )
- Scott - as
- Wes - as
53:09 - Arrays (Dog[] or Array)
- Scott - Dog[]
- Wes - Dog[]
54:02 - Assert or Generic (if both work)
- querySelector(’.thing’) as HTMLVideoElement; or querySelector(’.thing’);
- Scott - querySelector(’.thing’);
- Wes - querySelector(’.thing’);
- Syntax 324: TypeScript Fundamentals
- Syntax 327: Hasty Treat - TypeScript Compilers and Build Tools
- Axios
- VS Code
- Syntax 310: Serverless, Deno and TypeScript with Brian Leroux
- Cloudinary
- Notion
- Scott: Powerowl 16 Battery Recharger
- Wes: Fairywill Pro P11
- Scott: Level 2 Node Authentication - Sign up for the year and save 25%!
- Wes: Beginner Javascript - Use the coupon code ‘Syntax’ for $10 off!
- Scott’s Instagram
- LevelUpTutorials Instagram
- Wes’ Instagram
- Wes’ Twitter
- Wes’ Facebook
- Scott’s Twitter
- Make sure to include @SyntaxFM in your tweets
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