15. class Greeter { private greeting: string; constructor(message: string) { this.greeting = message; } public greet() { return 'Hello, ' + this.greeting; } } ! var greeter = new Greeter('world'); ! var button = document.createElement('button'); button.textContent = 'Say Hello'; button.onclick = () => { alert(greeter.greet()); }; ! document.body.appendChild(button); TS 16. var Greeter = (function