type-level-demo/09-type-programming

Type Programming in TypeScript

This example showcases advanced type-level programming in TypeScript using template literal types and recursive type definitions.

We can define a type that parses a string literal at compile-time to extract placeholders and construct a corresponding object type.

type ParseUrlParams<Url> = ...;

function navigate<P extends string>(path: P, params: ParseUrlParams<P>) {
  // ...
}

navigate("/book/{author}/{id}", { author: "foo", id: "bar" }); // Correct
navigate("/book/{author}/{id}", { author: "foo" }); // -> 💥 Compiler Error: missing 'id'

This allows for extremely type-safe APIs, where the parameters required for a function are derived directly from a string template, ensuring that developers provide all necessary data.