JavaScript Objects

In JavaScript, objects are used to represent real-world entities like a student, car, or book. They are a core part of Object-Oriented Programming (OOP) and allow you to store and manage related data and behaviors together.

What Is an Object?

An object is a collection of key-value pairs. Each key is called a property, and when a property stores a function, it’s called a method.

Objects are declared using curly braces {}, known as object literal syntax.

				
					let person = {
  name: "John",
  age: 30,
  greet: function () {
    return `Hello, my name is ${this.name} and I am ${this.age} years old.`;
  }
};

Accessing Object Properties

You can access properties in two ways:

				
					console.log(person.name);     // Dot notation → "John"
console.log(person["age"]);   // Bracket notation → 30

Both notations are valid. Bracket notation is useful when the key is stored in a variable or has spaces.

Modifying Objects

You can easily add, update, or delete properties from an object:

				
					person.address = "New York";           // Add
person["phone"] = "123-456-7890";      // Add
person.name = "Mike";                  // Update
delete person.age;                     // Delete

Object Methods

Objects can contain methods — functions defined inside the object:

				
					console.log(person.greet());
// Output: "Hello, my name is Mike and I am undefined years old."

(Notice that we deleted age earlier.)

Creating Objects Using Constructor Functions

You can also create objects using a constructor function — a function designed to initialize new objects using the new keyword:

				
					function Person(name, age) {
  this.name = name;
  this.age = age;
  this.greet = function () {
    return `Hello, my name is ${this.name} and I am ${this.age} years old.`;
  };
}

let person1 = new Person("Ali", 28);
let person2 = new Person("Areeba", 24);

console.log(person1.greet());

This is the foundation of classical OOP in JavaScript before ES6 classes.

Built-in Object Methods

JavaScript provides useful built-in methods for working with objects:

hasOwnProperty(prop) – checks if the object has a specific property.
toString() – returns a string representation of the object.
valueOf() – returns the primitive value of the object.

Example:

				
					console.log(person1.hasOwnProperty("name")); // true

Creating an Empty Object

You can also use the built-in Object() constructor to create an empty object:

				
					let emptyObj = new Object();
emptyObj.title = "Untitled";

Summary

Objects store data using key-value pairs.
You can use either object literals {} or constructor functions to create objects.
Objects can store both values and functions (methods).
Objects are the building blocks of JavaScript’s OOP model.

Understanding how to work with objects is essential for writing clean, organized, and reusable JavaScript code.