JavaScript Course

Objects Declaration and Properties

Objects Declaration

Simplify Objects with a Twist of Logic!

Imagine objects as boxes with labels and contents inside. An object's declaration is nothing but creating that box and labeling it with a unique name. Inside this box, you can store any type of data you want.

To declare an object in JavaScript, start with the curly braces {}. Instead of a label, we use a variable to reference this box. For instance:

const myObject = {};

Think of a Memory Game:

Just like you match cards in a memory game, you can match different values to different properties within an object.

const myObject = {
  name: "Afzal",
  age: 28,
  hobby: "Coding",

Next Up: Objects Properties

Now that we've set up the box, let's talk about filling it up with properties and their unique names. Stay tuned for our next section, where we'll explore the world of objects properties!

Objects Properties

What are Objects Properties?

Think of objects like a fancy to-do list. Each to-do item has a name (property) and a description (value).

Properties are like the labels on the to-do items. They give each piece of data a unique identity.

How to Access Object Properties?

Accessing properties is like opening up the to-do list and checking off items. You use the dot notation (.) or bracket notation ([]):

// Dot notation
console.log(; // Output: Afzal

// Bracket notation console.log(myObject["age"]); // Output: 28

Adding and Removing Properties

Adding a new property is like adding a new item to your to-do list:

myObject.favoriteFood = "Pizza";

Removing a property is like crossing off an item:

delete myObject.hobby;


  • Properties can store any data type, even objects or arrays.
  • Use dot notation for quick access when the property name is known.
  • Bracket notation is handy when the property name is dynamic or contains special characters.

What's Next?

Properties are the building blocks of objects. Next up, let's explore how to access them effectively in our programs, leaving you wondering... how do we dig into these property treasures?

Accessing Objects Properties

Unveiling the Treasure Trove of Object Properties

Accessing object properties is as simple as opening a treasure chest! Let's show you two ways to do it:

Dot Notation:

const myObject = {
  name: "Afzal",

console.log(; // Output: "Afzal"

Bracket Notation:

const myObject = {
  "full name": "Afzal Khan",

console.log(myObject["full name"]); // Output: "Afzal Khan"

Use dot notation when the property name is straightforward. However, bracket notation comes in handy when:

  • The property name has spaces or special characters.
  • The property name is stored in a variable.

Property Values: Adding and Removing Treasure

Adding a new property is like adding a new jewel to your treasure chest:

myObject.favoriteFood = "Pizza";

Removing a property is like tossing out an old trinket:

delete myObject.hobby;

Tips to Remember:

  • Object properties can store any treasure, including objects and arrays.
  • Use dot notation for quick access when you know the property name.
  • Bracket notation is your friend when dealing with dynamic property names or special characters.

Mysteries Unveiled

Now that you've discovered the secrets of accessing object properties, prepare to uncover even more hidden treasures in the next section: Adding and Removing Properties. Stay tuned!

Adding and Removing Properties

Dynamic Objects with Property Magic

Imagine an object as a magical box that can expand and shrink its contents. You can add new properties to your box like adding items to a shopping cart:

myObject.favoriteFood = "Pizza";

Similarly, removing a property is like taking items out of your box:

delete myObject.hobby;


  • Properties can store any type of data.
  • Use dot notation for quick access if the property name is known.
  • Bracket notation is useful when the property name is dynamic or contains special characters.

Next Stop: Objects Methods

Once you've mastered adding and removing properties, prepare to unleash the power of objects methods. They're like superpowers that make your objects come to life. Stay tuned for the next section, where the magic continues!

Objects Methods

Unveiling the Tools of Object Manipulation

Objects Methods are like secret powers that bring your objects to life. They allow you to perform actions on your objects, like:

  • Modifying properties
  • Returning values
  • Performing complex computations

Creating Methods

To create a method, use the following syntax:

myObject = {
  name: "Afzal",
  greet: function () {
    console.log("Hello, my name is " +;

In this example, we've created a method called greet() that logs a greeting message when called.

Accessing Methods

Access methods using the dot notation:

myObject.greet(); // Output: "Hello, my name is Afzal"


  • Methods are functions attached to objects.
  • They can take input parameters and return values.
  • Use the this keyword to access object properties within a method.

A Glimpse into the Methods Wonderland

Explore the marvels of objects methods in the next section, where we'll dive into the endless possibilities they offer. Stay tuned for Objects as Data Structures, where objects take on new forms and unleash their true power!

Objects as Data Structures

Objects Unleashed: Beyond Simple Storage

In the world of JavaScript, objects aren't just containers for data; they're versatile data structures that can store complex information and relationships. Let's explore this captivating aspect of objects:

A Deeper Dive into Objects

Just as buildings have rooms and floors, objects have properties and methods that organize and manage their data. But what sets objects apart is their ability to represent real-world entities, such as users, products, or even entire systems.

Imagine a user object: it could have properties like name, email, and address, and methods like login() or updatePassword(). This structure allows us to model and manipulate data in a logical and intuitive way.

The Power of Abstraction

Objects empower us to abstract away complex data structures. Instead of dealing with raw arrays or lists, we can create objects that represent these collections, making our code more readable and maintainable.

For example, instead of representing a list of products as a simple array:

const products = ["Apple", "Banana", "Orange"];

We can create an object-based representation:

const products = {
  fruits: ["Apple", "Banana", "Orange"],
  vegetables: ["Carrot", "Potato", "Onion"],
  dairy: ["Milk", "Cheese", "Yogurt"]

By organizing products into logical categories, we create a more structured and meaningful representation.

Stay Tuned for More...

Our journey into the world of objects continues! In the next section, we'll unravel the intriguing concept of Objects Immutability, where objects become unchangeable, paving the way for secure and reliable data handling.

Objects Immutability

Embracing Unchangeability for Data Integrity

In the realm of JavaScript, objects possess a fascinating attribute known as immutability. This means that once an object is created, its properties cannot be modified or deleted. This concept plays a crucial role in maintaining data integrity and ensuring the reliability of your applications.

Benefits of Immutability

  • Enhances Data Security: Immutable objects protect data from accidental or malicious changes, ensuring its integrity and accuracy.
  • Simplifies Reasoning: With immutable objects, you can be confident that the data within them will remain consistent throughout the program's execution, making it easier to reason about and debug your code.
  • Promotes Concurrency: Immutable objects can be shared across multiple threads or processes without the risk of data corruption, enabling concurrent access and increased efficiency.

How to Create Immutable Objects

JavaScript provides two ways to create immutable objects:

  1. Using Object.freeze() Method: The ext{Object.freeze()} method freezes an object, making its properties non-writable and non-configurable:

    const frozenObject = Object.freeze({ name: "Afzal" });
  2. Using the spread operator with Object.assign(): The spread operator (...) can be used with Object.assign() to create a new object with the same properties but immutable:

    const immutableObject = Object.assign({}, { name: "Afzal" });

Limitations of Immutability

While immutability offers numerous benefits, it also comes with certain limitations:

  • Inability to Update Data: Once an object becomes immutable, you cannot modify its properties. This can be a drawback in scenarios where you need to update or modify existing data.
  • Complexity in Handling Large Data: Immutable objects can lead to increased memory usage as they create new objects for any modification, which can be inefficient for large datasets.

Next Up: Objects Equality

Unraveling the Mysteries of Object Equality

In the next section, we'll explore the concept of object equality. We'll discover the different ways to compare objects and understand the nuances of strict equality versus loose equality. Stay tuned for more in-depth insights!

Objects Equality

Unlocking the Secrets of Object Comparison

In the realm of JavaScript, understanding object equality is essential for comparing and working with objects effectively. Let's dive into the two types of equality you'll encounter:

1. Strict Equality (===)

  • Compares both the value and type of objects.
  • Returns true only if both objects are the same value and have the same type.

2. Loose Equality (==)

  • Attempts to coerce objects into primitive values before comparing.
  • Returns true even if the objects have different types but have the same primitive value.

Practical Ways to Remember

  • Use === for strict comparisons: Ensures that you're comparing objects with the same value and type.
  • Avoid == for loose comparisons: It can lead to unexpected results due to type coercion.
  • Consider using for advanced comparisons: It provides a more comprehensive comparison algorithm.


// Strict equality
const obj1 = { name: "Afzal" };
const obj2 = { name: "Afzal" };
console.log(obj1 === obj2); // false (different memory addresses)

// Loose equality console.log(obj1 == obj2); // true (same primitive value)

// Using console.log(, obj2)); // false (different objects)


Understanding object equality is crucial for accurate object comparisons in JavaScript. Remember to use strict equality (===) for precise comparisons and to avoid loose equality (==) unless necessary. By mastering these concepts, you'll unlock the power of comparing objects effectively, leading to more robust and reliable code.

Next Step: Objects Iteration

Explore the fascinating world of object iteration in the next section, where we'll uncover the different ways to loop through objects and access their properties efficiently!

Objects Iteration

Unleashing the Power of Looping through Objects

In the realm of JavaScript, objects iteration empowers you to traverse through objects, accessing and manipulating their properties with ease. Let's explore the two primary methods of object iteration:

1. Loop

The loop iterates over the enumerable properties of an object:

const person = { name: "Afzal", age: 25 };
for (const key in person) {
  console.log(`${key}: ${person[key]}`);

This will log:

  • name: Afzal
  • age: 25

2. Object.keys() Method

The Object.keys() method returns an array of an object's enumerable property names:

const person = { name: "Afzal", age: 25 };
const keys = Object.keys(person);
for (const key of keys) {
  console.log(`${key}: ${person[key]}`);

This will also log:

  • name: Afzal
  • age: 25

Which Method to Use?

Choose the loop when you need to iterate over all enumerable properties, including inherited ones. Use Object.keys() when you want an array of only the object's own enumerable property names.

Next Adventure: Objects Prototype

In the upcoming section, we'll venture into the fascinating world of Objects Prototype, where we'll uncover the concept of inheritance and how objects can inherit properties and methods from their parent objects...

Objects Prototype

In the realm of JavaScript, objects come alive through their prototypes. Prototype is like a blueprint that provides a set of shared properties and methods to all objects that inherit from it. Imagine a parent blueprint that children objects follow to gain common traits.

Hierarchy Magic

With prototypes, objects can inherit properties and methods from their parent prototypes, and this inheritance continues up the family tree. It's like a family of objects, where children inherit from parents, and grandchildren inherit from both parents and grandparents.

How to Remember

  • Visualize objects as houses with different rooms (properties) and tools (methods).
  • Imagine each house having a blueprint (prototype) that contains the instructions for building it.
  • See children houses (objects) inheriting rooms and tools from their parent blueprints.

Code Example

// Parent prototype
const Person = {
  name: "John",
  age: 30,
  greet() {
    console.log(`Hi, my name is ${} and I'm ${this.age} years old.`);

// Child object const afzal = Object.create(Person);

// Inherited properties console.log(; // John console.log(afzal.age); // 30

// Inherited method afzal.greet(); // Hi, my name is John and I'm 30 years old.

Why Prototypes?

Prototypes are powerful because:

  • They allow for code reuse and maintainability: Common properties and methods can be inherited, reducing the need for repetitive code.
  • They promote encapsulation: Prototypes hide implementation details from child objects, enhancing security and flexibility.
  • They support polymorphism: Objects from different prototypes can respond differently to the same method call, allowing for dynamic behavior in code.

So, in the world of JavaScript, objects are not just isolated entities; they're connected through a tapestry of prototypes, forming a rich hierarchy that empowers them to inherit and share traits, making your code more efficient and elegant.

Next Chapter: Classes in JavaScript

Buckle up for the next adventure - Classes in JavaScript! Classes offer an exciting new way to define objects, with enhanced features and a more concise syntax. Get ready to delve into the depths of object-oriented programming in JavaScript!

Classes in JavaScript

Understanding Classes

In JavaScript, classes provide a powerful way to define and create objects with well-defined properties and methods. Classes are a newer feature introduced in ES6, offering a more concise and organized approach to object-oriented programming.

Benefits of Classes

  • Code Reusability: Classes allow you to create templates for objects, enabling code reuse and reducing the need for repetitive code.
  • Encapsulation: Classes encapsulate data and methods within a single unit, providing better control and organization.
  • Inheritance: Classes support inheritance, allowing you to create child classes that inherit properties and methods from parent classes.

Class Syntax

class Person {
  constructor(name, age) { = name;
    this.age = age;

greet() { console.log(Hello, my name is ${} and I am ${this.age} years old.); } }

  • Constructor: The constructor method is called when a new instance of a class is created.
  • this Keyword: The this keyword refers to the current object being created.
  • Properties and Methods: Properties and methods are defined within the class body.

Creating Instances

// Create a new Person object
const afzal = new Person("Afzal", 25);

// Access properties and methods console.log(; // "Afzal" afzal.greet(); // "Hello, my name is Afzal and I am 25 years old."

Extending Classes (Inheritance)

class Employee extends Person {
  constructor(name, age, title) {
    super(name, age); // Call the parent constructor
    this.title = title;

work() { console.log(I am ${this.title} and my name is ${}.); } }

  • extends: This keyword specifies the parent class the child class inherits from.
  • super: The super keyword calls the constructor of the parent class.

Real-World Example

// Define a class for a simple shopping cart
class ShoppingCart {
  constructor() {
    this.items = [];

addItem(item) { this.items.push(item); }

removeItem(item) { const index = this.items.indexOf(item); if (index > -1) { this.items.splice(index, 1); } }

calculateTotal() { return this.items.reduce((total, item) => total + item.price, 0); } }

// Create a shopping cart const cart = new ShoppingCart();

// Add items to the shopping cart cart.addItem({ name: "Apple", price: 1.5 }); cart.addItem({ name: "Orange", price: 2.0 });

// Calculate the total cost of the items in the cart const total = cart.calculateTotal();

// Print the total cost console.log(Total cost: ${total});

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