typescript define function on type code example

Example 1: typescript default parameter

function sayName({ first, last = 'Smith' }: {first: string; last?: string }): void {
  const name = first + ' ' + last;
  console.log(name);
}

sayName({ first: 'Bob' });

Example 2: typescript function type

interface Date {
  toString(): string;
  setTime(time: number): number;
  // ...
}