javascript-packages/packages/typescript-types

Typescript Types

A utility types library for Typescript.

Types

The types included in this library are categorized by their purpose.

Test Types

Type	Description
IsAny<T>	true if T is any, false otherwise (null, undefined also yield false)
IsNever<T>	true if T is never, false otherwise (null, undefined, any also yield false)
If<Test, TrueBranch, FalseBranch>	Returns TrueBranch if Test is true, FalseBranch otherwise1 .
[IsKeyOf<T, K>][]	true if K is a key of T, false otherwise. If T is any, any K but never will yield true.
[IsEmptyString<S>][]	true if S is the empty string '', false otherwise.2

Extraction Types

Type	Description
OptionalKeysOf<T>	A union of all keys of T that are marked as optional. If T is a union, a union of the optional keys of all union members of T is returned3 .

Combination Types

Type	Description
Assign<Shape, Defaults, Obj>	Return a type with the structure of Shape and value types from Obj or Default for missing optional keys in Obj.

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1. If boolean is passed as Test the return value is a union of both branches, i.e. TrueBranch | FalseBranch. ↩︎

2. If T is any will yield true, as it is taken to be any string. ↩︎

3. If T is any, it returns a union of string and number 'string | number'. ↩︎