JavaScript Objects

Objects are variables too, but they can contain multiple values. In real life, a car is an object. A car has properties like weight and color, and methods like start and stop.

Object Definition

You define (and create) a JavaScript object with an object literal using curly braces {}.

const person = {
  firstName: "Mim",
  lastName: "Akter",
  age: 25,
  eyeColor: "brown"
};

Object Properties

The name:value pairs in JavaScript objects are called properties.

Accessing Object Properties

You can access object properties in two ways:

1. Dot Notation (.)

This is the most common and readable way.

console.log(person.firstName); // "Mim"

2. Bracket Notation ([])

This is useful if the property name is stored in a variable or contains spaces.

console.log(person["firstName"]); // "Mim"

Object Methods

Objects can also have methods. Methods are actions that can be performed on objects. A method is simply a property containing a function definition.

const person = {
  firstName: "Mim",
  lastName: "Akter",
  fullName: function() {
    return this.firstName + " " + this.lastName;
  }
};

console.log(person.fullName()); // "Mim Akter"

Key Points to Remember

• Objects are collections of properties and methods
• Properties are written as name:value pairs
• Access properties using dot notation or bracket notation
• Methods are functions stored as object properties
• The this keyword refers to the current object
• Always use const when declaring objects as standard practice

Common Mistakes to Avoid

Try It: A Shopping Cart Item

A second example — an object with both data and a method that uses that data:

const cartItem = {
    name: "Wireless Mouse",
    price: 25,
    quantity: 2,
    subtotal: function() {
        return this.price * this.quantity;
    }
};

console.log(cartItem.subtotal()); // 50

Frequently Asked Questions