Prototypal Inheritance and Classes 
function Person(name) {
  this.name = name;
}
Person.prototype.sayHi = function () {
  console.log("Hi, I'm " + this.name);
};

class Student extends Person {
  constructor(name, grade) {
    super(name);
    this.grade = grade;
  }
  showGrade() {
    console.log(`${this.name}'s grade is ${this.grade}`);
  }
}

const s = new Student("Roshini", "A");
s.sayHi();
s.showGrade();

Object and Array Destructuring

const user = { name: "Roshini", age: 20 };
const { name, age } = user;
console.log(name, age);

const arr = [10, 20];
const [a, b] = arr;
console.log(a, b);



Modules
Steps:

Create math.js:

 
export function add(x, y) {
  return x + y;
}
Create main.js:

 
import { add } from "./math.js";
console.log(add(5, 3));
Add <script type="module" src="main.js"></script> in HTML


 Function Generators and Symbols
function* countUp() {
  yield 1;
  yield 2;
  yield 3;
}
let gen = countUp();
console.log(gen.next().value);

const sym1 = Symbol("id");
console.log(sym1 === Symbol("id")); // false

Closure

function outer() {
  let count = 0;
  return function () {
    count++;
    console.log("Count:", count);
  };
}
const counter = outer();
counter(); // 1
counter(); // 2