Understanding Objects in JavaScript

As we start learning JavaScript, we first work with variables and arrays. Arrays are useful when we want to store a list of values in order.

But sometimes data is not just a list — it has different pieces of information related to one thing.

For example, imagine you want to store information about a person.

You might have:

• name

• age

• city

If we try to store this using separate variables, it looks like this:

let name = "Aryan";
let age = 21;
let city = "Nagpur";

This works, but these variables are not grouped together. They represent one person but are stored separately.

This is where objects become useful.

An object lets us store related data together using key-value pairs.

What is an Object?

An object is a collection of key-value pairs.

Example:

let person = {
  name: "Aryan",
  age: 21,
  city: "Nagpur"
};

Here:

• name, age, and city are keys (properties)

• "Aryan", 21, "Nagpur" are values

You can think of an object like a profile card that holds different pieces of information about something.

Creating an Object

Objects are created using curly braces {}.

Example:

let person = {
  name: "Aryan",
  age: 21,
  city: "Nagpur"
};

Each property inside the object follows this format:

key : value

Multiple properties are separated by commas.

Accessing Object Properties

We can access values inside an object in two ways.

1. Dot Notation

This is the most common and simplest way.

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

Output:

Aryan
21

---

2. Bracket Notation

Another way is using square brackets.

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

Output:

Nagpur

Bracket notation is useful when the property name is stored inside a variable.

Example:

let key = "name";
console.log(person[key]);

Updating Object Properties

We can change a value by assigning a new one.

Example:

person.age = 22;

console.log(person.age);

Output:

22

Here we simply replaced the old value.

Adding New Properties

Objects are flexible. We can add new properties anytime.

Example:

person.country = "India";

console.log(person);

Now the object becomes:

{
  name: "Aryan",
  age: 22,
  city: "Nagpur",
  country: "India"
}

Deleting Properties

If we want to remove a property, we use the delete keyword.

Example:

delete person.city;

console.log(person);

Now the city property is removed.

Looping Through an Object

Sometimes we want to see all properties inside an object.

For that we use the for...in loop.

Example:

let person = {
  name: "Aryan",
  age: 21,
  city: "Nagpur"
};

for (let key in person) {
  console.log(key, person[key]);
}

Output:

name Aryan
age 21
city Nagpur

Here:

• key represents each property name

• person[key] gives the value

Array vs Object

Beginners often get confused between arrays and objects.

Here is a simple comparison.

Array	Object
Stores ordered values	Stores key-value pairs
Access using index	Access using property name
Example: list of items	Example: information about one item

Example array:

let fruits = ["Apple", "Banana", "Mango"];

Example object:

let person = {
  name: "Aryan",
  age: 21
};

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

Practice Assignment

Try this exercise to understand objects better.

1. Create a Student Object

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

2. Update One Property

student.age = 21;

3. Add a New Property

student.city = "Pune";

4. Print All Keys and Values

for (let key in student) {
  console.log(key, student[key]);
}