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Objects in JavaScript

What are Objects in JavaScript?

In JavaScript, an object is a collection of properties and methods that are used to model real-world entities. Objects are used to store data, represent complex structures, and define methods. They are a fundamental building block of JavaScript and are used extensively in web development, mobile development, and other areas of software development.

Creating Objects

In JavaScript, there are several ways to create objects. The most common way is using the object literal notation:

let myObject = {
  key1: "value1",
  key2: "value2",
  key3: "value3"

Another way to create an object is using the Object() constructor:

let myObject = new Object();
myObject.key1 = "value1";
myObject.key2 = "value2";
myObject.key3 = "value3";

You can also use the object destructuring method which is a bit more advanced:

const myObject = {key1, key2, key3};

Properties and Methods

Properties are the values stored within an object and can be accessed using dot notation or bracket notation. For example, the following two lines of code are equivalent:


Methods are functions that are stored as properties within an object. They can be invoked using the dot notation or bracket notation, just like properties.

let myObject = {
  key1: "value1",
  key2: "value2",
  key3: "value3",
  myMethod: function() {
    console.log("This is my method");



JavaScript uses prototype-based inheritance, which means that objects can inherit properties and methods from other objects. Every object in JavaScript has a prototype, which is an object from which it inherits properties and methods. The prototype of an object can be accessed using the __proto__ property.

let myObject = {
  key1: "value1",
  key2: "value2",
  key3: "value3"

let mySecondObject = Object.create(myObject);
console.log(mySecondObject.key1); // "value1"

The code above creates a new object, mySecondObject, which inherits properties from myObject.

Object Types in JavaScript

JavaScript has several built-in object types, including:

  • Object: the base object type

  • Array: an object that stores a collection of items

  • Function: an object that represents a function

  • String: an object that represents a string

  • Number: an object that represents a number

  • Boolean: an object that represents a boolean value

  • Date: an object that represents a date and time

  • RegExp: an object that represents a regular expression

Additionally, developers can create their custom object types by using constructor functions or classes.

Most Common Uses and Examples

Objects are used for many different purposes in JavaScript, but some of the most common uses include:

  • Storing data, such as user information or application settings

  • Representing complex structures, such as a game board or a shopping cart

  • Defining methods, such as event handlers or validation logic

Here are a few examples of how objects are used in JavaScript:

// A simple object that stores user information
let user = {
  name: "John Doe",
  email: "[email protected]",
  age: 30

// A more complex object that represents a shopping cart
let cart = {
  items: [
    { name: "item1", price: 12.99 },
    { name: "item2", price: 24.99 },
    { name: "item3", price: 9.99 }
  total: function() {
    let sum = 0;
    for (let i = 0; i < this.items.length; i++) {
      sum += this.items[i].price;
    return sum;


Object Limitations and Nuances

Objects in JavaScript have some limitations and nuances that developers should be aware of:

  • JavaScript was originally created for functional programming, which means it doesn't have all the features of traditional object-oriented programming languages. For more complex projects, developers often turn to other solutions to address these issues.

  • JavaScript objects are loosely typed, which means that properties and methods can be added or removed dynamically at runtime.

  • JavaScript objects are mutable, which means that their properties and methods can be modified at any time.

  • The null value is often used to represent the absence of an object, but it can cause confusion and lead to errors if not handled properly.


  • Objects are a fundamental building block of JavaScript and are used to model real-world entities.

  • They are used to store data, represent complex structures, and define methods.

  • We have covered the basics of object creation, properties, methods, and inheritance.

  • Understanding the concept of objects is important for language fluency and for building more complex and powerful applications.

  • We also discussed some limitations and nuances of objects in JavaScript and the different built-in object types.

With this knowledge, you'll have a firm grasp of the basics and the ability to confidently experiment with them in your projects.