Classes & Objects in JavaScript

6/29/2025
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Diagram explaining JavaScript classes and objects

Classes & Objects in JavaScript

Classes & Objects in JavaScript

In JavaScript, classes and objects are foundational to writing modular and reusable code using Object-Oriented Programming (OOP) principles. They allow developers to model real-world entities, group functionality, and maintain cleaner code.

What is a Class in JavaScript?

A class is a blueprint for creating objects. Introduced in ES6 (ECMAScript 2015), the class syntax provides a more readable and structured way to work with constructor functions and prototypes under the hood.

Example: Creating a Class

class Person {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }

  greet() {
    console.log(`Hi, I'm ${this.name} and I'm ${this.age} years old.`);
  }
}

  • constructor() is a special method used to initialize object properties.

  • greet() is an instance method available to all objects created from the class.

What is an Object?

An object is an instance of a class. It represents a specific entity created using the structure defined by the class.

Example: Creating an Object

const john = new Person("John", 30);
john.greet(); // Hi, I'm John and I'm 30 years old.

Here, john is an object created using the Person class — it has access to both the properties and methods defined in that class.

Key Concepts in JavaScript Classes

Instance Properties

Defined in the constructor() and unique to each object.

Methods

Functions defined inside the class and shared across instances via prototype.

this Keyword

Refers to the object being created or used.

Inheritance with Classes

Classes in JavaScript support inheritance using the extends and super keywords.

class Animal {
  constructor(name) {
    this.name = name;
  }

  speak() {
    console.log(`${this.name} makes a sound`);
  }
}

class Dog extends Animal {
  speak() {
    console.log(`${this.name} barks`);
  }
}

const dog = new Dog("Buddy");
dog.speak(); // Buddy barks

Benefits of Using Classes in JavaScript

  • Cleaner and more structured code.

  • Easier inheritance and method sharing.

  • Better code organization and maintainability.

  • Syntactic sugar over prototype-based inheritance.

Conclusion

Classes and objects are essential parts of modern JavaScript development. Classes provide the structure, while objects are the actual data instances. With ES6 class syntax, JavaScript makes OOP more accessible, letting developers build cleaner, more maintainable code.

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