Inheritance

With ES2015, there is also a simplified syntax to use inheritance between classes. Let's look at an example:

class ITBook extends Book { // {1} 
  constructor(title, pages, isbn, technology) { 
    super(title, pages, isbn); // {2} 
    this.technology = technology; 
  } 
 
  printTechnology() { 
    console.log(this.technology); 
  } 
} 
let jsBook = new ITBook('Learning JS Algorithms', '200', '1234567890', 'JavaScript'); 
console.log(jsBook.title); 
console.log(jsBook.printTechnology()); 

We can extend another class and inherit its behavior using the keyword extends (line {1}). Inside the constructor, we can also refer to the constructor superclass using the keyword super (line {2}).

Although the syntax of this new way of declaring classes in JavaScript is very similar to other programming languages such as Java and C/C++, it is good to remember that JavaScript object-oriented programming is done through a prototype.