type-fest

Breaking

• breaking

  This package is now pure ESM. Please read this.

• breaking

  Require TypeScript 5.9 b5b0214

• breaking

  Require Node.js 20 cc2b0f2

• breaking

  Reminder: type-fest requires strict: true in your tsconfig.

• breaking

  StringKeyOf: Rename to KeyAsString e492c9c

• breaking

  ArrayTail: Enable preserveReadonly by default and remove the option b34b1d8

• breaking

  CamelCase / CamelCasedProperties / CamelCasedPropertiesDeep / PascalCase / PascalCasedProperties / PascalCasedPropertiesDeep: Disable preserveConsecutiveUppercase by default 8226c1b

  • This aligns it with the general JavaScript naming convention.

• breaking

  PartialDeep: Disable allowUndefinedInNonTupleArrays by default b3c4524

• breaking

  Split: Enable strictLiteralChecks by default 544a846

• breaking

  Paths: Default maxRecursionDepth 5 (was 10) 2ab5dec

• breaking

  ObservableLike: Move to sub-export 2a1072e

• deprecated

  Deprecate If* types in favor of a single If 4c2151a

New types

• Alphanumeric — Single alphanumeric character (A–Z, a–z, 0–9). 484e030

• AllExtend — Evaluates to true if every element of a tuple/array extends U. c8c6d55

• ConditionalSimplify — Simplifies a type’s unions/intersections with opt-in controls. b7a4771

• ConditionalSimplifyDeep — Deep version of ConditionalSimplify that recurses into objects. b7a4771

• DigitCharacter — Single ASCII digit character (0–9). 484e030

• ExcludeStrict — Non-distributive, stricter variant of Exclude<T, U>. e6f62a2

• ExtendsStrict — Non-distributive A extends B check. d71242a

• ExtractStrict — Non-distributive, stricter variant of Extract<T, U>. 98d24fa

• IsLowercase — Evaluates to true if a string literal is all lowercase. afe132c

• IsNullable — Evaluates to true if T includes null. 5067e25

• IsOptional — Evaluates to true if T includes undefined. 5067e25

• IsOptionalKeyOf — Evaluates to true if property K of T is optional. 93728b5

• IsReadonlyKeyOf — Evaluates to true if property K of T is readonly. 93728b5

• IsRequiredKeyOf — Evaluates to true if property K of T is required. 93728b5

• IsUnion — Evaluates to true if T is a union type. b3d92ed

• IsUndefined — Evaluates to true if the type is exactly undefined. f7bc576

• IsUppercase — Evaluates to true if a string literal is all uppercase. afe132c

• LowercaseLetter — Single lowercase Latin letter (a–z). 484e030

• RemovePrefix — Removes a specified prefix from a string literal. 18a1c04

• UppercaseLetter — Single uppercase Latin letter (A–Z). 484e030

Improvements

• Jsonify: Handle unknown as JsonValue 642bb13

• SetRequired / SetOptional / SetReadonly: Handle functions with properties a5e45d4

• Schema: Preserve arrays/remove extraneous unions 8a96def; drop undefined for recurseIntoArrays 1cb955b

• ReadonlyKeysOf / WritableKeysOf: Add object constraint a6efbe0

• TsConfigJson: Add TypeScript 5.9 fields d2bda94

Fixes

• Or: Fix with boolean, never, any 42d6106

• And: Fix with boolean, never, any b38ac60

• IsStringLiteral: Fix uncollapsed unions, and tagged types eb37799 / d1b35c7

• Paths: Fix behavior with index signatures 9926e5d

• ConditionalKeys: Fix behavior with arrays and unions 4d7cc50

• RequiredDeep: Fix with undefined bfcdbc4

• Split: Fix template strings ending with interpolation 853b881

• ArrayTail: Fix fix non-tuple arrays f3aabd8

• Fix UnionMin and UnionMax d52d5e7

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