TypeScript

Template Literal Types

type World = "world";

type Greeting = `hello ${World}`;

// type Greeting = "hello world"

type EmailLocaleIDs = "welcome_email" | "email_heading";
type FooterLocaleIDs = "footer_title" | "footer_sendoff";

type AllLocaleIDs = `${EmailLocaleIDs | FooterLocaleIDs}_id`;

// type AllLocaleIDs = "welcome_email_id" | "email_heading_id" | "footer_title_id" | "footer_sendoff_id"

type AllLocaleIDs = `${EmailLocaleIDs | FooterLocaleIDs}_id`;
type Lang = "en" | "ja" | "pt";

type LocaleMessageIDs = `${Lang}_${AllLocaleIDs}`;

// type LocaleMessageIDs = "en_welcome_email_id" | "en_email_heading_id" | "en_footer_title_id" | "en_footer_sendoff_id" | "ja_welcome_email_id" | "ja_email_heading_id" | "ja_footer_title_id" | "ja_footer_sendoff_id" | "pt_welcome_email_id" | "pt_email_heading_id" | "pt_footer_title_id" | "pt_footer_sendoff_id"

type Greeting = "Hello, world"
type ShoutyGreeting = Uppercase<Greeting> //Capitalize<LowercaseGreeting> | Uncapitalize<UppercaseGreeting>

// type ShoutyGreeting = "HELLO, WORLD"

type ASCIICacheKey<Str extends string> = `id-${Lowercase<Str>}`
type MainID = ASCIICacheKey<"MY_APP">

// type MainID = "id-my_app"