How to convert the first letter of a string literal type into an uppercase format or capitalize in TypeScript?

February 10, 2022 - 1 min read

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 😃!

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