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I like the tricks :) – Kasia

Laser-focused types

@RiccardoOdone•Suggest a tip•

Even if it gets verbose, encoding the rules of the domain in your types will prevent impossible values.

type PostCode = string
const shipTo = (postCode: PostCode) => {}
shipTo("pwned") // ⛔️ Invalid postCode

const shipTo = (postCode: PostCode) => {
  PostCodeModule.format(postCode) // ✅ Encapsulated responsibility
}

// postcode.ts
type Digit = "1" | "2" | "3" | "4" | "6" | "7" | "8" | "9" | "0"
type PostCode = [Digit, Digit, "-", Digit, Digit, Digit]
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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