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 stuff
03:30 - any vs unknown
06:20 - never
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
34:14 - TypeScript without TypeScript (JSDoc / TSDoc)
40:08 - Interfaces vs Types
How we write TypeScript
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)
52:38 - Type Assertion (as or )
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’);
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