In JavaScript, objects are one of the most powerful ways to store and organize data.

Sometimes storing values in separate variables is not practical.

Example:

let name = "Rahul";
let age = 21;
let city = "Delhi";

This works, but managing related information separately becomes difficult.

Instead, JavaScript provides objects, which allow us to store related data together.

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What Are Objects?

An object is a collection of key-value pairs.

Example structure:

key : value

Example object:

let person = {
  name: "Rahul",
  age: 21,
  city: "Delhi"
};

Here:

Key	Value
name	Rahul
age	21
city	Delhi

So the object groups related information together.

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Why Objects Are Needed

Objects help developers:

• Organize related data

• Represent real-world entities

• Make code more readable

Example: representing a person.

let person = {
  name: "Amit",
  age: 25,
  city: "Mumbai"
};

Instead of multiple variables, everything is stored inside one object.

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Creating Objects

Objects are created using curly braces {}.

Example:

let car = {
  brand: "Toyota",
  model: "Camry",
  year: 2022
};

This object contains three properties.

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Accessing Object Properties

We can access object values in two ways.

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Dot Notation

The most common way.

let person = {
  name: "Amit",
  age: 25,
  city: "Mumbai"
};

console.log(person.name);

Output:

Amit

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Bracket Notation

Another way to access properties.

console.log(person["age"]);

Output:

25

Bracket notation is useful when property names are dynamic.

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Updating Object Properties

We can change existing values easily.

Example:

let person = {
  name: "Amit",
  age: 25
};

person.age = 26;

console.log(person.age);

Output:

26

The value changed from 25 → 26.

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Adding New Properties

Objects can grow by adding new properties.

Example:

let person = {
  name: "Amit",
  age: 25
};

person.city = "Mumbai";

console.log(person);

Output:

{
  name: "Amit",
  age: 25,
  city: "Mumbai"
}

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Deleting Properties

We can remove properties using the delete keyword.

Example:

let person = {
  name: "Amit",
  age: 25,
  city: "Mumbai"
};

delete person.city;

console.log(person);

Output:

{
  name: "Amit",
  age: 25
}

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Looping Through Object Keys

Sometimes we want to access all properties of an object.

We can use a for...in loop.

Example:

let person = {
  name: "Amit",
  age: 25,
  city: "Mumbai"
};

for (let key in person) {
  console.log(key + ": " + person[key]);
}

Output:

name: Amit
age: 25
city: Mumbai

This loop goes through every key in the object.

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Difference Between Array and Object

Feature	Array	Object
Structure	Ordered list	Key-value pairs
Access	Index (0,1,2)	Property name
Use Case	Lists of items	Structured data

Example array:

let fruits = ["apple", "banana", "orange"];

Example object:

let fruit = {
  name: "apple",
  color: "red"
};

Arrays are used for lists, while objects are used for structured information.

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Assignment Practice

Create a Student Object

let student = {
  name: "Ravi",
  age: 20,
  course: "Computer Science"
};

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Update a Property

student.age = 21;

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Loop Through Keys and Values

for (let key in student) {
  console.log(key + ": " + student[key]);
}

Output:

name: Ravi
age: 21
course: Computer Science

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Visual Idea of Object Structure

Example object:

student
│
├── name  → Ravi
├── age   → 21
└── course → Computer Science

This shows how objects store data in key-value pairs.

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