To convert the first letter of string literal type into an uppercase format or capitalize, you can use the built-in Capitalize type that comes with TypeScript.
TL;DR
// string literal type
type Greeting = "hello";
// convert first letter of
// string literal type
// into uppercase format or capitalize
type GreetingCapitalized = Capitalize<Greeting>; // Hello
For example, let's say we have a string literal type like this,
// string literal type
type Greeting = "hello";
Now to capitalize the string literal type let's use the Capitalize built-in type and pass the Greeting type into it using the angled bracket (<>) syntax.
It can be done like this,
// string literal type
type Greeting = "hello";
// convert first letter of
// string literal type
// into uppercase format or capitalize
type GreetingCapitalized = Capitalize<Greeting>; // Hello
Now if you hover over the GreetingCapitalized type you can see that the hello string literal type is now capitalized. Yay 🥳.
See the above code live in codesandbox.
That's all 😃!