TypeScript in the Browser

Version

{
  const output = document.getElementById('version_output')! as HTMLPreElement;
  output.innerHTML = `
ts.version: ${ts.version}
`
}

number test

let num: number = 123;
{
  const output = document.getElementById('number_output')! as HTMLPreElement;
  output.innerHTML += JSON.stringify({num});
}

greeter test

interface Person {
  firstName: string;
  lastName: string;
}

function greeter(person: Person) {
  return "Hello, " + person.firstName + " " + person.lastName;
}

let user = { firstName: "Jane", lastName: "User" };
{
  const output = document.getElementById('greeter_output')! as HTMLPreElement;
  output.textContent += greeter(user);
}