In JavaScript, objects are one of the most important data structures. They allow you to store data in key–value pairs and represent real-world entities — like users, products, or configurations — in a structured way.

Objects are everywhere in JavaScript — from browser APIs to JSON data, and even built-in features like Math and Date. Let’s explore them step by step.

What Is an Object?

An object in JavaScript is a collection of properties, where each property has a key (name) and a value.

Syntax

let objectName = {
  key1: value1,
  key2: value2,
  key3: value3
};

Each key is a string (or symbol), and each value can be any data type — a number, string, boolean, array, another object, or even a function!

Example

Let’s create a simple person object:

let person = {
  name: "Harry",
  age: 22,
  isStudent: true
};

Here:

• "name" is a key with the value "Harry".
• "age" is a key with the value 22.
• "isStudent" is a key with the value true.

Accessing Object Properties

There are two ways to access properties of an object:

1. Dot Notation

console.log(person.name); // Output: Harry

2. Bracket Notation

console.log(person["age"]); // Output: 22

Use dot notation when you know the property name beforehand. Use bracket notation when the property name is dynamic or stored in a variable.

Example with Dynamic Property

let key = "isStudent";
console.log(person[key]); // Output: true

Here, since the key is stored in a variable, we must use bracket notation.

Modifying and Adding Properties

You can modify existing properties or add new ones anytime — objects in JavaScript are mutable.

Modify a Property

person.age = 23;
console.log(person.age); // Output: 23

Add a New Property

person.city = "Delhi";
console.log(person.city); // Output: Delhi

Deleting Properties

To remove a property from an object, use the delete operator:

delete person.isStudent;
console.log(person);
// Output: { name: "Abhinav", age: 23, city: "Delhi" }

Nested Objects

Objects can contain other objects — allowing you to represent complex data structures.

let user = {
  name: "Riya",
  address: {
    city: "Mumbai",
    zip: 400001
  }
};
 
console.log(user.address.city); // Output: Mumbai

You can nest objects as deeply as needed.

Objects and Functions

Functions can be stored inside objects — these are called methods.

let calculator = {
  add: function(a, b) {
    return a + b;
  },
  subtract(a, b) {
    return a - b; // shorthand syntax
  }
};
 
console.log(calculator.add(5, 3));      // 8
console.log(calculator.subtract(10, 4)); // 6

This is one of the key features that makes objects so versatile in JavaScript.

Looping Through an Object

You can iterate through an object’s properties using a for...in loop.

let car = {
  brand: "Tesla",
  model: "Model 3",
  year: 2023
};
 
for (let key in car) {
  console.log(key + ": " + car[key]);
}

Output:

brand: Tesla
model: Model 3
year: 2023

Useful Object Methods

JavaScript provides several built-in methods to work with objects:

Example

let car = { brand: "Toyota", year: 2020 };
 
console.log(Object.keys(car));    // ["brand", "year"]
console.log(Object.values(car));  // ["Toyota", 2020]
console.log(Object.entries(car)); // [["brand", "Toyota"], ["year", 2020]]

Objects vs Arrays

Sometimes, you’ll even combine them — like an array of objects:

let users = [
  { name: "Abhinav", age: 22 },
  { name: "Priya", age: 25 },
  { name: "Rahul", age: 28 }
];
 
console.log(users[0].name); // Output: Abhinav