fucctions.ts

function greet(person: string, date: Date): void {
  console.log(`Hello, ${person}! Today is ${date.toDateString()}.`);
}

const getFullName = (first: string, last?: string): string =>
  last ? `${first} ${last}` : `${first}`;

let fullName = getFullName("John");
greet(fullName, new Date());

fullName = getFullName("John", "Doe");
greet(fullName, new Date());