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What Are Classes in JavaScript?

JavaScript classes are templates used to create objects with shared properties and methods. Introduced in ES6, classes make object-oriented programming in JavaScript easier to read, write, and maintain.
Behind the scenes, JavaScript classes still use prototype-based inheritance, but the class syntax provides a cleaner and more familiar structure—especially for beginners.

Why Use Classes in JavaScript?

Using classes in JavaScript helps you:
  • Organize code in a structured way
  • Reuse logic across multiple objects
  • Build scalable applications
  • Improve readability and maintenance
  • Model real-world entities easily
Classes are widely used in frontend frameworks, Node.js backend development, and large web applications.

Creating a Class in JavaScript

A class is created using the class keyword.
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class User {
  constructor(name, role) {
    this.name = name;
    this.role = role;
  }

  greet() {
    return `Hello, I am ${this.name}`;
  }
}
  • constructor() initializes object data
  • Methods define behavior
  • this refers to the current object
Creating Objects from a Class
Once a class is defined, you can create objects using the new keyword.
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const user1 = new User("John", "Developer");
const user2 = new User("Alex", "Designer");
Each object gets its own data but shares the same methods.
Constructor Method in JavaScript Classes
The constructor is a special method that runs automatically when an object is created.
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constructor(name, role) {
  this.name = name;
  this.role = role;
}
You can pass values into the constructor to initialize object properties.
Class Methods
Methods define actions that objects can perform.
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greet() {
  return `Welcome ${this.name}`;
}
Class methods are automatically added to the prototype, improving performance.
Inheritance Using Classes
Inheritance allows one class to extend another class using the extends keyword.
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class Admin extends User {
  accessLevel() {
    return "Full Access";
  }
}
This lets the child class reuse functionality from the parent class.
Using super() in JavaScript Classes
The super() method calls the parent class constructor.
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class Admin extends User {
  constructor(name) {
    super(name, "Admin");
  }
}
This is required before accessing this in a subclass.
Public vs Private Fields in Classes
Modern JavaScript supports private class fields using #.
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class Account {
  #balance = 0;

  deposit(amount) {
    this.#balance += amount;
  }

  getBalance() {
    return this.#balance;
  }
}
This helps achieve encapsulation.

Classes vs Constructor Functions

Before ES6, classes were created using constructor functions. ES6 classes provide the same functionality with cleaner syntax.
Classes are easier to understand, especially for beginners learning object-oriented JavaScript.

When Should You Use JavaScript Classes?

JavaScript classes are ideal when:
  • Building large applications
  • Managing reusable components
  • Creating backend logic in Node.js
  • Structuring complex data models
For small scripts, simple objects or functions may be sufficient.

Final Thoughts

JavaScript classes simplify object-oriented programming by providing a clean and structured syntax. Mastering classes will help you build scalable, professional-level JavaScript applications.
JavaScript OOP
JavaScript Constructors