ch1.md

Core OOP in JavaScript - 1st Edition

Chapter 1: Instantiation(new keyword) in JavaScript

What is instantiation in OOP?

According to the Cambridge dictionary, the English meaning of Instantiation is "something that represents or is an example of something else.

Our definition: Instantiation in OOP is a process of creating an object from a given structure/blueprint(constructor).

Creating an instance of a constructor

We use the new keyword to create an instance

new World();

What does the new keyword do?

• Tells Js engine that the function is not a regular function but a constructor therefore create a blank object called the this object.
• Injects the constructor prototype into the this object to make the prototype fields accessible by the constructor instance.
• Returns this object if the constructor doesn't return an explicit object.

For more on constructor in js

Code snippet on JavaScript instantiation

function Country(name) {
  this.name = name;
  this.defaultGreeting = "Hello!"

  this.greet = function () {
    if (this.name === "Estonia") return "Tere!";
    
    return this.defaultGreeting;
  };
}


const estonia = new Country("Estonia");
console.log("Estonia says", estonia.greet());

const germany = new Country("Germany");
console.log("Germany says", germany.greet());