Make functions in interface optionnal code example

Example 1: typescript interface function

interface IEmployee {
    empCode: number;
    empName: string;
    getSalary: (number) => number; // arrow function
    getManagerName(number): string; 
}

Example 2: typescript class interface

interface IPerson {
  name: string
  age: number
  hobby?: string[]
}

class Person implements IPerson {
  name: string
  age: number
  hobby?: string[]

  constructor(name: string, age: number, hobby: string[]) {
    this.name = name
    this.age = age
    this.hobby = hobby
  }
}

const output = new Person('john doe', 23, ['swimming', 'traveling', 'badminton'])
console.log(output)