Capitalize

In this medium-level challenge, you'll implement Capitalize<T> which converts the first letter of a string to uppercase and leave the rest as-is.

type capitalized = Capitalize<'hello world'> // expected to be 'Hello world'

Detailed Explanation

type MyCapitalize<S extends string> = S extends `${infer First}${infer Rest}`
  ? `${Uppercase<First>}${Rest}`
  : S

How it works:

• First, we constrain the type S to be a string with extends string
• S extends ${infer First}${infer Rest} matches the string type and captures the first letter into First and the rest of the string into Rest
• ? ${Uppercase<First>}${Rest} returns the string with the first letter capitalized
• : S returns the string if it doesn't start with a letter

This challenge helps you understand TypeScript's template literal types and how to apply this concept in real-world scenarios.