[javascript] What is the 'new' keyword in JavaScript?

Javascript is not object oriented programming(OOP) language therefore the LOOK UP process in javascript work using 'DELEGATION PROCESS' also known as prototype delegation or prototypical inheritance.

If you try to get the value of a property from an object that it doesn't have, the JavaScript engine looks to the object's prototype (and its prototype, 1 step above at a time) it's prototype chain untll the chain ends upto null which is Object.prototype == null (Standard Object Prototype). At this point if property or method is not defined than undefined is returned.

Thus with the new keyword some of the task that were manually done e.g

1. Manual Object Creation e.g newObj.
2. Hidden bond Creation using proto (aka: dunder proto) in JS spec [[prototype]] (i.e. proto)
3. referencing and assign properties to newObj
4. return of newObj object.

All is done manually.

function CreateObj(value1, value2) {
  const newObj = {};
  newObj.property1 = value1;
  newObj.property2 = value2;
  return newObj;
}
var obj = CreateObj(10,20);

obj.__proto__ === Object.prototype;              // true
Object.getPrototypeOf(obj) === Object.prototype // true

Javascript Keyword new helps to automate this process:

1. new object literal is created identified by this:{}
2. referencing and assign properties to this
3. Hidden bond Creation [[prototype]] (i.e. proto) to Function.prototype shared space.
4. implicit return of this object {}

function CreateObj(value1, value2) {
  this.property1 = value1;
  this.property2 = value2;
}

var obj = new CreateObj(10,20);
obj.__proto__ === CreateObj.prototype             // true
Object.getPrototypeOf(obj) == CreateObj.prototype // true

Calling Constructor Function without the new Keyword:

=> this: Window

function CreateObj(value1, value2) {
  var isWindowObj = this === window;
  console.log("Is Pointing to Window Object", isWindowObj);
  this.property1 = value1;
  this.property2 = value2;
}
var obj = new CreateObj(10,20); // Is Pointing to Window Object false
var obj = CreateObj(10,20); // Is Pointing to Window Object true
window.property1; // 10
window.property2; // 20