funky ts with template literal types and satisfies

#microposts

TIL you can do some funky stuff with satisfies and template literal types in TS.

const startWithA = {
  1: "a",
  2: "ab",
  3: "abc",
} satisfies Record<number, `a${string}`>;

const names = ["bob", "john"] as const;
type Hello = "Hello";
type Name = (typeof names)[number];
type TL = `${Hello} ${Name}`;
const greetings = ["Hello john", "Hello bob", "Hello walter"] as const;

greetings.forEach((g) => {
  g satisfies TL;
});