class-interface.ts

interface Human {
    firstName: string;
    lastName: string;
		name?: Function;
		isLate?(time: Date): Function;
}

class Person  implements Human {
    constructor(public firstName, public lastName) {
    }

    public name() {
        return `${this.firstName} ${this.lastName}`;
    }

    protected whoAreYou() {
        return `Hi i'm ${this.name()}`;
    }
}

class Student extends Person {
    course;

    constructor(firstName, lastName, course) {
        super(firstName, lastName);
        this.course = course;
    }

    whoAreYou() {
        return `${super.whoAreYou()} and i'm studying ${this.course}`;
    }
}

let asim = new Student("Asim", "Hussain", "typescript");
console.log(asim.whoAreYou());