# Understanding Objects in JavaScript

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:

```javascript
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.

* * *

# What Are Objects?

An **object** is a collection of **key-value pairs**.

Example structure:

```plaintext
key : value
```

Example object:

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

Here:

| Key | Value |
| --- | --- |
| name | Rahul |
| age | 21 |
| city | Delhi |

So the object **groups related information together**.

* * *

# Why Objects Are Needed

Objects help developers:

*   Organize related data
    
*   Represent real-world entities
    
*   Make code more readable
    

Example: representing a person.

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

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

* * *

# Creating Objects

Objects are created using **curly braces** `{}`.

Example:

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

This object contains **three properties**.

* * *

# Accessing Object Properties

We can access object values in two ways.

* * *

# Dot Notation

The most common way.

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

console.log(person.name);
```

Output:

```plaintext
Amit
```

* * *

# Bracket Notation

Another way to access properties.

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

Output:

```plaintext
25
```

Bracket notation is useful when property names are dynamic.

* * *

# Updating Object Properties

We can change existing values easily.

Example:

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

person.age = 26;

console.log(person.age);
```

Output:

```plaintext
26
```

The value changed from **25 → 26**.

* * *

# Adding New Properties

Objects can grow by adding new properties.

Example:

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

person.city = "Mumbai";

console.log(person);
```

Output:

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

* * *

# Deleting Properties

We can remove properties using the `delete` keyword.

Example:

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

delete person.city;

console.log(person);
```

Output:

```javascript
{
  name: "Amit",
  age: 25
}
```

* * *

# Looping Through Object Keys

Sometimes we want to access **all properties of an object**.

We can use a **for...in loop**.

Example:

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

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

Output:

```plaintext
name: Amit
age: 25
city: Mumbai
```

This loop goes through **every key in the object**.

* * *

# 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:

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

Example object:

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

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

* * *

# Assignment Practice

## Create a Student Object

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

* * *

# Update a Property

```javascript
student.age = 21;
```

* * *

# Loop Through Keys and Values

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

Output:

```plaintext
name: Ravi
age: 21
course: Computer Science
```

* * *

# Visual Idea of Object Structure

Example object:

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

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

* * *