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Prevent mutations

@RiccardoOdone•Suggest a tip•

You can add Readonly to prevent unwanted mutations.

const sortArray = (xs: number[]) => xs.sort()
const xs = [3, 1, 2]

console.log(xs) // [3, 1, 2]
console.log(sortArray(xs)) // [1, 2, 3]
console.log(xs) // ⛔️ [1, 2, 3]

const sortArray = (xs: Readonly<number[]>) =>
  xs.sort() // ✅ Does not compile

const sortArray = (xs: Readonly<number[]>) =>
  [...xs].sort()
const xs = [3, 1, 2]

console.log(xs) // [3, 1, 2]
console.log(sortArray(xs)) // [1, 2, 3]
console.log(xs) // ✅ [3, 1, 2]
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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