Power Tools: Typed Arrays & Union Types

Enemy 1 of 5

You've already seen arrow functions written without types elsewhere, and typed functions using the function keyword. This is where the two meet: an arrow function can be typed just as fully as a regular one, with parameter types and a return type — (n: number): number => n * n.

TypeScript checks that the parameter and return types match wherever the arrow function is called, exactly as it would for a function written with the function keyword — the shorter arrow syntax doesn't cost you any type safety, it's purely a different way to write the same thing.