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Parse, don't cast

@RiccardoOdone•Suggest a tip•

APIs could return something that doesn't adhere to your expected response. It's always a good idea to parse values at the boundary of the system before they are sent in.

fetch(URL)
  .then(res => res.json())
  .then((user: User) => ...) // ⛔️

fetch(URL)
  .then(res => res.json())
  .then(json => parse(json)) // ✅
  .then(parsed => {
    if (parsed.success) {
      // Exactly what's expected
    } else {
      // Must handle bad response
    }
  })
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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