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Enumerating statuses

@RiccardoOdone•Suggest a tip•

Explicitly enumerate the valid responses in a union type instead of adding boolean flags.

type Response = { fetched: boolean, errored: boolean, data?: Data }
const response: Response = // ⛔️ Error before fetch?!
  { fetched: false, errored: true, data: null }

// ⛔️ There are more combinations that don't make any sense.

type Response<Error, Success> =
  { _kind: 'not_requested' } |
  { _kind: 'loading' } |
  { _kind: 'error', error: Error } |
  { _kind: 'success', data: Success }

const response: Response = // ✅ Does not compile.
  { fetched: false, errored: true, data: null }
Type-safe carouselDo not throwFilter using a type assertionUse precise typesType-safe string templatingEnumerating a union typeNumbers with unitsZero nullEnumerating statusesAnd typesAvoiding window as anyUse descriptive valuesCheck authorization with typesExtract union types from record typesKeep in sync with conditional typesType-safe pickPass arguments by namePick instead of duplicatingPrevent mutationsType aliasesModel with different typesPrefer static types over testsPush conditionals downType-level functionsCheck Authorization With Types (again)From Union to TupleLimit typesLaser-focused typesCallable typesPartial considered harmfulSatisfy typesWTH?!Parse, don't castNarrow typesFetch footgunModel with different types (2)Polymorphic typesParse, don't cast (again)Type-safe envObject vs Recordconst Type ParametersDigType checksExpand intellisenseNumbers with units (2)Unchecked indexed accessExtract instead of duplicating

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