How do I declare a NodeJs module in Typescript?

Question

My consuming Node code looks like this:

var helloworld = require('helloworld');
helloworld.sayhello();

Using the Typescript goodness, how would I declare the module exporting the sayhello() function?

Answer 1

helloworld.ts

export function sayhello() {
    console.log('hello, world!');
}

Note that you would not write a containing module block (the file itself is the module).