When working with JavaScript, we often need to store related pieces of information together.

For example, imagine we want to store information about a person:

• Name

• Age

• City

We could store them in separate variables:

let name = "Alex";
let age = 25;
let city = "Mumbai";

But this becomes messy as the program grows. A better way is to group related data together.

This is where objects come in.

In this article, we’ll learn:

• What objects are and why they are useful

• How to create objects

• How to access properties (dot notation and bracket notation)

• How to update object properties

• How to add and delete properties

• How to loop through object keys

All examples are simple and beginner-friendly, so you can try them in your browser console or Node.js.

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What Are Objects?

An object is a way to store data in key-value pairs.

Think of it like a dictionary:

Key	Value
name	"Alex"
age	25
city	"Mumbai"

Each piece of information has:

• a key (the label)

• a value (the data)

In JavaScript, an object looks like this:

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

Here:

• name, age, city → keys

• "Alex", 25, "Mumbai" → values

Together they form a person object.

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Objects vs Arrays

Before going further, it’s helpful to understand the difference between arrays and objects.

Array

Arrays store values using index numbers.

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

Accessing elements:

fruits[0]; // apple

---

Object

Objects store values using keys.

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

Accessing elements:

person.name; // Alex

So the key difference:

• Arrays → index based

• Objects → key based

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Creating Objects

Objects are created using curly braces {}.

Example:

let person = {
  name: "Rahul",
  age: 22,
  city: "Kolkata"
};

console.log(person);

Output:

{ name: 'Rahul', age: 22, city: 'Kolkata' }

This object stores three properties.

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Accessing Object Properties

There are two ways to access object properties:

1. Dot notation

2. Bracket notation

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Dot Notation

This is the most common and simplest way.

let person = {
  name: "Rahul",
  age: 22,
  city: "Kolkata"
};

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

Output:

Rahul
22

We simply write:

object.property

---

Bracket Notation

Another way is using square brackets.

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

Output:

Kolkata

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

Example:

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

Output:

Rahul

---

Updating Object Properties

We can change the value of an existing property easily.

Example:

let person = {
  name: "Rahul",
  age: 22
};

person.age = 23;

console.log(person.age);

Output:

23

Here we updated the age from 22 to 23.

---

Adding New Properties

We can also add new properties to an object.

Example:

let person = {
  name: "Rahul",
  age: 22
};

person.city = "Delhi";

console.log(person);

Output:

{ name: 'Rahul', age: 22, city: 'Delhi' }

The object now contains a new property called city.

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Deleting Properties

We can remove properties using the delete keyword.

Example:

let person = {
  name: "Rahul",
  age: 22,
  city: "Delhi"
};

delete person.city;

console.log(person);

Output:

{ name: 'Rahul', age: 22 }

The city property was removed.

---

Looping Through Object Keys

Sometimes we want to loop through all properties of an object.

We can do this using a for...in loop.

Example:

let person = {
  name: "Rahul",
  age: 22,
  city: "Kolkata"
};

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

Output:

name Rahul
age 22
city Kolkata

How it works:

• key represents each property name

• person[key] gives the value

So the loop goes through every key-value pair.

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Objects are one of the most important concepts in JavaScript because they help us organize related data.

Key takeaways:

• Objects store data in key-value pairs

• They are created using {}

• Properties can be accessed using dot notation or bracket notation

• You can update, add, or delete properties

• You can loop through object properties using for...in