class constructor javascript

1class Person {
2  constructor(name, age) {
3    this.name = name;
4    this.age = age;
5  }
6}
7
8const person = new Person("John Doe", 23);
9
10console.log(person.name); // expected output: "John Doe"

1<script>
2   class Student {
3      constructor(rno,fname,lname){
4         this.rno = rno
5         this.fname = fname
6         this.lname = lname
7         console.log('inside constructor')
8      }
9      set rollno(newRollno){
10         console.log("inside setter")
11         this.rno = newRollno
12      }
13   }
14   let s1 = new Student(101,'Sachin','Tendulkar')
15   console.log(s1)
16   //setter is called
17   s1.rollno = 201
18   console.log(s1)
19</script>

1A constructor is a function that creates an instance of a class
2  which is typically called an “object”. In JavaScript, a constructor gets 
3  called when you declare an object using the new keyword.
4  The purpose of a constructor is to create an object and set values if 
5  there are any object properties present.
6

1// Improved formatting of Spotted Tailed Quoll's answer
2class Person {
3	constructor(name, age) {
4		this.name = name;
5		this.age = age;
6	}
7	introduction() {
8		return `My name is ${name} and I am ${age} years old!`;
9	}
10}
11
12let john = new Person("John Smith", 18);
13console.log(john.introduction());

1    class Cat {
2        constructor(name, age) {
3            this.name = name;
4            this.age = age;
5        }
6      
7      	get fullname() {
8          return this.getFullName()
9        }
10        getFullName() {
11            return this.name + ' ' + this.age
12        }
13    }
14
15    const run = document.getElementById("run");
16    run.addEventListener("click", function () {
17        let Skitty = new Cat('Skitty', 9);
18        let Pixel = new Cat('Pixel', 6);
19        console.log(Skitty.getFullName()); // Skitty 9
20      	console.log(Skitty.fullname); // Skitty 9 => shorter syntax
21        console.log(Skitty, Pixel); 
22      // Object { name: "Skitty", age: 9} Object {name: "Pixel", age:6}
23    })

1class prettyMixedGirl {
2    constructor(name, age, ethnicity, phoneNumber) {
3        this.name = name;
4        this.age = age;
5        this.ethnicity = ethnicity;
6        this.phoneNumber = phoneNumber;
7    }
8    // Method
9    hi() {
10        console.log(`Hi! My name is ${this.name}. I am ${this.age} years old. My ethnicity is ${this.ethnicity}. My phone number is ${this.phoneNumber}`);
11    }
12}
13// Create new object out of Constructor (Instantiate)
14const ashley = new prettyMixedGirl('Ashley', 28, 'Dominican Republican', '313-218-1345');
15const luna = new prettyMixedGirl('Luna', 26, 'Chilean', '718-231-1343');
16
17// Initiate a method
18ashley.hi(); // Hi! My name is Ashley. I am 28 years old. My ethnicity is Dominican Republican. My phone number is 313-218-1345
19luna.hi(); // Hi! My name is Luna. I am 26 years old. My ethnicity is Chilean. My phone number is 718-231-1343