Uppercase<StringType>

INFO

The Uppercase<StringType> utility type is available starting from TypeScript version 4.1. For more information see in TypeScript Handbook, Release Note

Overview

The Uppercase<StringType> utility type in TypeScript is used to convert each character in the string to the uppercase version.

Syntax

type Uppecase<S extends string> = intrinsic;

• StringType (S): The string that you want to convert each character in the string to the uppercase version.

Examples

Example #1

type Greeting = 'Hello, world';
type ShoutyGreeting = Uppercase<Greeting>; // "HELLO, WORLD"

type ASCIICacheKey<Str extends string> = `ID-${Uppercase<Str>}`;
type MainID = ASCIICacheKey<'my_app'>; // "ID-MY_APP"

Example #2

type HttpMethod = 'get' | 'post' | 'patch' | 'delete';

type ErrorMessageTypes = {
  [Method in HttpMethod as Uppercase<Extract<Method, string>>]?: { [Pattern: string]: string };
};

const errorMessages: ErrorMessageTypes = {
  GET: {
    '/posts': 'Failed to retrieve posts.',
    '/posts/:id': 'Failed to retrieve the specific post.',
  },
  // POST, PATCH, DELETE
};