JavaScript object basics

In JavaScript, objects are complex data structures that allow you to store and organize related data and functionality in a single entity. Objects are composed of key-value pairs, where the keys are strings or symbols and the values can be of any data type, including other objects. Here's an in-depth explanation with examples:

Creating Objects

Objects can be created using the object literal syntax, by enclosing key-value pairs within curly braces {}.

let person = { firstName: "John", lastName: "Doe", age: 30, isStudent: false };

Accessing Object Properties

Object properties can be accessed using dot notation or square brackets.

console.log(person.firstName); // Output: "John" console.log(person["age"]); // Output: 30

Modifying Object Properties

Object properties can be modified by assigning new values to them.

person.age = 32; person["isStudent"] = true;

Adding New Properties

You can add new properties to an object at any time. = "New York"; person["gender"] = "Male";

Nested Objects

Objects can contain other objects as their properties, forming nested structures.

let address = { street: "123 Main St", city: "Los Angeles", zipCode: "90001" }; person.address = address; console.log(; // Output: "Los Angeles"

Methods in Objects

Objects can also have methods, which are functions stored as properties.

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

Object Constructors (Classes)

You can use constructor functions to create multiple instances of objects with shared properties and methods.

function Person(firstName, lastName) { this.firstName = firstName; this.lastName = lastName; } let person1 = new Person("Alice", "Smith"); let person2 = new Person("Bob", "Johnson");

ES6 Class Syntax

ES6 introduced a more class-like syntax for creating objects.

class Car { constructor(make, model) { this.make = make; this.model = model; } } let myCar = new Car("Toyota", "Camry");


Objects are a foundational concept in JavaScript, providing a way to model real-world entities, organize data, and encapsulate functionality within a single unit, contributing to the modularity and maintainability of your code.