Basics Of Classes in JavaScript| Constructions

JavaScript Classes are templates for JavaScript Objects. Use the keyword class to create a class. Always add a method named constructor():
Syntax

class ClassName {
constructor() { … }
}

Example

class Car {
constructor(name, year) {
 this.name = name;
 this.year = year;
}
}

The example above creates a class named “Car”. The class has two initial properties: “name” and “year“.
A JavaScript class is not an object. It is a template for JavaScript objects.

Using a Class

When you have a class, you can use the class to create objects:
Example

let myCar1 
= new Car("Ford", 2014);
let myCar2 
= new Car("Audi", 2019);

The example above uses the Car class to create two Car objects.

The Constructor Method


The constructor method is called automatically when a new object is created. The constructor method is a special method:

  • It has to have the exact name “constructor”
  • It is executed automatically when a new object is created
  • It is used to initialize object properties.

If you do not define a constructor method, JavaScript will add an empty constructor method.

Class Methods

Class methods are created with the same syntax as object methods. Use the keyword class to create a
class. Always add a constructor() method. Then add any number of methods.


Syntax

class ClassName {
constructor() { ... }
 method_1() { ... }
 method_2() { ... }
 method_3() { ... }
}

Create a Class method named “age”, that returns the Car age:
Example

class Car {
constructor(name, year) {
 this.name = name;
 this.year = year;
}
age() {
 let date = new Date();
 return date.getFullYear() -
this.year;
}
}
let myCar 
= new Car("Ford", 2014);
document.getElementById("demo").
innerHTML =
"My car is " + myCar.age() + " 
years old.";

You can send parameters to Class methods:
Example

class Car {
constructor(name, year) {
 this.name = name;
 this.year = year;
}
 age(x) {
 return x - this.year;
}
}
let date = new Date();
let year = date.getFullYear();
let myCar 
= new Car("Ford", 2014);
document.getElementById("demo").
innerHTML=
"My car is " + myCar.age(year) 
+ " years old."

Basics Of Classes in JavaScript| Constructions
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