Intrinsic String Manipulation Types

例

code:ts

type EnthusiasticGreeting<T extends string> = ${Uppercase<T>}

type HELLO = EnthusiasticGreeting<"hello">;

// same as

// type HELLO = "HELLO";

code:ts

type T10 = Uppercase<'hello'>; // "HELLO"

type T11 = Lowercase<'HELLO'>; // "hello"

type T12 = Capitalize<'hello'>; // "Hello"

type T13 = Uncapitalize<'Hello'>; // "hello"

type T20 = Uppercase<'foo' | 'bar'>; // "FOO" | "BAR"

type T21 = Lowercase<'FOO' | 'BAR'>; // "foo" | "bar"

type T22 = Capitalize<'foo' | 'bar'>; // "Foo" | "Bar"

type T23 = Uncapitalize<'Foo' | 'Bar'>; // "foo" | "bar"

type T30<S extends string> = Uppercase<aB${S}>;

type T31 = T30<'xYz'>; // "ABXYZ"

type T32<S extends string> = Lowercase<aB${S}>;

type T33 = T32<'xYz'>; // "abxyz"

type T34 = ${Uppercase<'abc'>}${Lowercase<'XYZ'>}; // "ABCxyz"

type T40 = Uppercase<string>; // string

type T41 = Uppercase<any>; // any

type T42 = Uppercase<never>; // never

type T43 = Uppercase<42>; // Error, type 'number' does not satisfy the constraint 'string'

定義を直接見に行っても見れない、処理系依存の型になっている

code:ts

type Uppercase<S extends string> = intrinsic;