Compile-time casing
Derive uppercase labels or messages from string literal types.
TypeScript · Type Alias
Uppercase
Uppercase<StringType> converts every character in a string type to its uppercase form. It is an intrinsic compiler type commonly used with template literal types to derive uppercase string formats.
- Since
- 4.1
How it works
Uppercase is an intrinsic string manipulation type that transforms every character in a string type to its uppercase version. It is evaluated by the compiler and is useful inside template literal types for deriving consistently capitalized string formats.
Syntax
Uppercase<StringType>Parameters
| Name | Type | Description |
|---|---|---|
StringType | string type | The string type whose characters should be converted to uppercase. |
Returns
A string type with every character converted to its uppercase version.
Key points
- Uppercase changes every character in the supplied string type, not only its first character.
- For the literal "Hello, world", the resulting type is the exact literal "HELLO, WORLD".
- Uppercase belongs to a group of four built-in casing aliases.
Common mistakes
- Uppercase is compiler-provided rather than a user-visible declaration in the standard .d.ts files.
Example: Uppercase a string literal type
type Greeting = "Hello, world";
type ShoutyGreeting = Uppercase<Greeting>;
const greeting: ShoutyGreeting = "HELLO, WORLD";
console.log(greeting);This compiles because Uppercase transforms every character in the literal type to its uppercase form.
When to use it
Formatted cache keys
Create normalized identifiers such as ID-MY_APP from generic input.
Typed key generation
Build APIs whose string keys follow an uppercase convention.
Related
LowercaseCapitalizeUncapitalizeTemplate Literal Types