Length of String

In this medium-level challenge, you'll compute the length of a string literal, which behaves like String.length.

Detailed Explanation

type LengthOfString<
  S extends string,
  Count extends string[] = [],
> = S extends `${infer First}${infer Rest}`
  ? LengthOfString<Rest, [...Count, First]>
  : Count['length']

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
• ? LengthOfString<Rest, [...Count, First]> recursively calls LengthOfString with the rest of the string and the first letter
• : Count['length'] returns the length of the string

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