class Phone {
    model: string = ""
}

class Employee {
    firstName: string = ""
    lastName: string = ""
    phone: Phone = null
}

let nokiaPhone = new Phone()
nokiaPhone.model = "Nokia 6610"

let kim = new Employee()
kim.firstName = "Victorya"
kim.lastName = "Kim"
kim.phone = nokiaPhone

console.log(kim.phone.model)