class Person {

    constructor(n, a) {

        var p = this;

        p.n = n;

        p.a = a;

        p.total = 0;

        p.a.map(x => p.total += parseInt(x)); //get total salary     

    }

    firstName() {

        return this.n = "Min Min ";

    }

    displayMsg() {

        return " and My yearly income is " + this.total;

    }

}

​

class Employee extends Person {

    constructor(name, age) {

        super(name, age);

        this.name = name;

    }

    lastName() {

        return this.name;

    }

    Show() {

        return "My name is " + super.firstName() + this.lastName() + super.displayMsg();

    }

}

emp = new Employee("David", [123, 456, 754]);

console.log(emp.Show());