What is a Class?

In JavaScript, a Class is essentially a blueprint for creating objects. Before ES6 (ECMAScript 2015), JavaScript developers had to use functions and the prototype chain to achieve object-oriented programming. Classes provide a much cleaner, more intuitive syntax for doing this.

You can think of a class like an architectural blueprint for a house. The blueprint itself isn't a house, but it tells you exactly how to build one.

Defining a Class

To define a class in JavaScript, you use the class keyword followed by the name of the class. By convention, class names should always start with a capital letter (PascalCase).

class User {
    // We will define properties and methods here
    login() {
        console.log("User has logged in.");
    }
}

Now that we have a User class, we can create actual user objects (instances) from it.

const himanshu = new User();
himanshu.login(); // Outputs: "User has logged in."

Why Use Classes?

When you are building large applications, you will often need to create many objects that share the same structure. For example, in a blog application, every single article will have a title, an author, and content. Instead of writing out an object from scratch every time, a Post class ensures every article is built correctly and shares the same methods.

💡 Himanshu's Tip:

Under the hood, JavaScript classes are actually "syntactic sugar" over JavaScript's existing prototype-based inheritance. This means JavaScript isn't a traditional class-based language like Java or C++, but the class syntax makes it much easier to write and read Object-Oriented code!

Interview Questions

1. What is the difference between a class and an object?
2. Were classes always a part of JavaScript? If not, when were they introduced?
3. What naming convention should you use when naming a class?