class-inheritence-javascript.js

class Person {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }
  printIdentity() {
    return "Mr. " + this.name;
  }
  testFunc() {
    console.log("I am test from person");
  }
}

class Student extends Person {
  constructor(std, name, age) {
    super(name, age);
    this.std = std;
  }
  printGreeting() {
    return super.printIdentity() + " is in standard " + this.std;
  }
  testFunc() {
    console.log("I am test from student");
  }
}

class HeadBoy extends Student {
  constructor(house, std, name, age) {
    super(std, name, age);
    this.house = house;
  }
  print() {
    return (
      super.printGreeting() +
      " and is in house " +
      this.house +
      " he is " +
      this.age +
      " years old"
    );
  }
  /*testFunc() {//uncommenting this function will invoke test func from headboy
    console.log('I am test from head boy')
  }*/
}

let headboy = new HeadBoy("gandhi", "10th", "kamlesh", 20);
headboy.testFunc();

Prototype chain for this -

Interesting this to note here is that ES6 class keyword is just syntactical sugar over the JavaScript prototypical inheritance.

another interesting point is that if you define functions outside of constructor like its done in this this example, all those functions will be available on the prototypes and not on the object directly.