Classes & Inheritance.md

Classes & Inheritance

ES6 supports classes using class keyword, for constructor constructor keyword and for the inheritance using extends keyword.

Table of Contents

1. Classes
2. Construtor & Inheritance

Classes

You cannot call a class like a normal function. But you can use new keyword to invoke a class.

Demo

class Parent {
	print() {
		 console.log('I am a class');
	}
}

Parent(); //Type error: Cannot call a class as a function

var myParent = new Parent(); //Use `new` keyword to use class as construtor

new Parent().print(); //print I am a class

Note: Class declarations are not hoisted like a function declaration and will be avaiable only after its execution. See the below example

##### Hoisting Example

Demo

new myClass().print(); //TypeError due to hoisting limitation in class

class myClass {
		print() {
		console.log('I am a class with a name myClass');
	}
}

new myClass().print(); //print I am a class with a name myClass

⬆ back to top

Construtor & Inheritance

Using class we can create a base class or parent class which can be later inherited by an another class. See an example below.

Demo

//Parent class
class Parent {
	constructor(myName) {
		this.name = myName;
	}
	
	print() {
		return 'My parent is ' + this.name;
	}
}

//Child class inheriting from a base class
class Child extends Parent {
	constructor(myName, newName) {
		super(myName); //Calling derived constructor using `super`
		this.newName = newName;
	}
	
	print() {
		console.log(super.print() + ' and My name is ' + this.newName);
	}
}

let myChild = new Child('Gokul', 'Krishh');

myChild.print(); //print My parent is Gokul and My name is Krishh

⬆ back to top

Reference

• es6 classes