Local types

The TypeScript type system allows us to declare types (such as type aliases, classes, and interfaces) within the declaration of functions and methods. In the early releases of TypeScript, this was not allowed:

interface Person {
    name: string;
    age: number;
}

function makePerson(name: string, age: number): Person {

    // Local type
    class Person implements Person {
        constructor(
            public name: string,
            public age: number
        ) {}
    }

    return new Person(name, age);

}

let user = makePerson("Remo", 28);