typescript_narrowing_1.ts

class Person {
	name: string;

	constructor(name: string) {
		this.name = name;
	}
}

class Employee extends Person {
	salary: number;

	constructor(name: string, salary: number) {
		super(name);
		this.salary = salary;
	}

	getYearlySalary() {
		return 12 * this.salary;
	}
}

class Manager extends Person {
	employees: Employee[];

	constructor(name: string, employees: Employee[]) {
		super(name);
		this.employees = employees;
	}

	getYearlySalariesOfAllEmployees() {
		let salary = 0;
		this.employees.forEach(employee => {
			salary += employee.getYearlySalary();
		});

		return salary;
	}
}