javascript class constructor

class Car {
 
  constructor(brand) {
    this.carname = brand;
 
  }
  present() {
   
    return "I have a " + this.carname;
 
  }
}

mycar = new Car("Ford");
document.getElementById("demo").innerHTML 
  = mycar.present();
 class Person {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }
}

const person = new Person("John Doe", 23);

console.log(person.name); // expected output: "John Doe"'use strict' 
class Polygon { 
   constructor(height, width) { 
      this.h = height; 
      this.w = width;
   } 
   test() { 
      console.log("The height of the polygon: ", this.h) 
      console.log("The width of the polygon: ",this. w) 
   } 
} 

//creating an instance  
var polyObj = new Polygon(10,20); 
polyObj.test();      <script>
   class Student {
      constructor(rno,fname,lname){
         this.rno = rno
         this.fname = fname
         this.lname = lname
         console.log('inside constructor')
      }
      set rollno(newRollno){
         console.log("inside setter")
         this.rno = newRollno
      }
   }
   let s1 = new Student(101,'Sachin','Tendulkar')
   console.log(s1)
   //setter is called
   s1.rollno = 201
   console.log(s1)
</script>