using-classes.ts

class Greeter {
  greeting: string;
  constructor(message: string) {
    this.greeting = message;
  }
  greet() {
    return "Hello, " + this.greeting;
  }
}

let greeter = new Greeter("world");

let button = document.createElement("button");
button.textContent = "Say Hello";
button.onclick = function() {
  alert(greeter.greet());
};

document.body.appendChild(button);