Announcing TypeScript 1.0(blogs.msdn.com)

    interface Person {
        firstname: string;
        lastname: string;
    }

    function greeter(person: Person) {
        return 'Hello, ' + person.firstname + ' ' + person.lastname;
    }

    var user = {firstname: 'John', lastname: 'Doe'}

    document.body.innerHTML = greeter(user);

    // function signature
    getNumber(context: any, callback: (result: Number) => void);
    
    // calling that function
    // unfortunately, here the type of num is any
    // unless I specify it manually
    getNumber(..., (num) => { ... });