hello.ts

#!/usr/bin/env typescript

class Greeter {
  name: string;

  constructor(name?: string) {
    this.name = name || 'Nobody';
  }   
  say_hello() {
    console.log("Hello " + this.name);
  }
}

var greeter = new Greeter();
greeter.say_hello();
var greeter = new Greeter('There');
greeter.say_hello();

/*
Hello Nobody 
Hello There
*/