TypeScript Fundamentals — Getting a Bit Deeper


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
        • someValue

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)

  • 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’);
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