Public, Private and Protected Variables:
=========================================
variable_name = value ==> Public type
_variableNname = value ==> Private
__variableName = value ==> Protected

public type of variables can allow to access in any where
private type limit to the class only. ( We can access within the same class)
protected type can be limit to package

Object Property Methods:
========================
1) Object.defineProperty():
===========================
==> Object ==> collection of properties.
==> defineProperty() can use to add new property to the existed object.
==> defineProperty() can also use to modify the existing property of object.
Syntax:
	Object.defineProperty(ObjectName, property, description)

Here:
	ObjectName ==> name of the object on which we need to use "defineProperty()".
	property ==> name of the property(key) must be specify in string format.
	description ==> value for the specified key

==> We can allow to define attributes for Objects while creating with defineProperty().
	1) value ==> for assigning a value to the given property
	2) writable 
		specify: true ==> if the property allowed for modification
			 false==> if the property consider for only reading but not to modify.
	3) configurable
		specify: true
			 false

// using defineProperty() for creating the new Object

let userProfile = {};

Object.defineProperty(userProfile,'userName',{
    value : "Jatin Das",
    writable : true,
    configurable : true
});

console.log(userProfile);
console.log(userProfile.userName);
userProfile.userName = "Ashok Jain";
console.log(userProfile.userName);
delete userProfile.userName;
console.log(userProfile.userName);

=================================================
// using defineProperty() for creating the new Object

let userProfile = {};

Object.defineProperty(userProfile,'userName',{
    value : "Jatin Das",
    writable : true,
    configurable : false
});

// defining new property
let ageValue = 30;

Object.defineProperty(userProfile,'age',{
    // getter method
    get(){
        console.log("Getting the user age...");
        return ageValue;
    },
    
    // setter method
    set(newAge){
        console.log("Setting the value for user age...");
        ageValue = newAge;
    },
    configurable : false
});

console.log(userProfile.age);
userProfile.age = 31;
console.log(userProfile.age);

delete userProfile.age;
console.log(userProfile.age);
==========================================
Object.getOwnPropertyNames():
============================
==> return an array with only the property names of an object.
Syntax:
	Object.getOwnPropertyNames(object-name);


Object.keys():
=============
==> return an array with keys of the specified object.
Syntax:
	Object.keys()

let person = {
    firstName : "John",
    lastName : "Justin",
    age : 55,
    eyeColor : "blue"
}

console.log(person);

let properties = Object.getOwnPropertyNames(person);
console.log(properties);

let keys = Object.keys(person);
console.log(keys);