TypeScript Fundamentals — Getting a Bit Deeper [Syntax]

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

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

34:14 - TypeScript without TypeScript (JSDoc / TSDoc)