Classes

While JavaScript is heavily prototype-based and makes it incredibly easy to create one-off object literals (POJOs), Classes provide a structured, reusable template for creating multiple objects that share the same properties and methods.

The Class Syntax

You define a class using the class keyword.

class User {
  // The constructor is called whenever a new instance is created
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }
}

// Instantiate the class using the 'new' keyword
const user = new User("Lane", 100);

console.log(user.name); // Output: "Lane"

How It Works

1. class declaration: Creates the blueprint.
2. constructor(): A special, reserved method name. It is automatically executed when a new instance of the class is created. It is primarily used to set up the initial state (this.name = ...).
3. new keyword: This tells JavaScript to allocate memory for a brand new object, invoke the constructor, and bind the this keyword inside the class to that specific new object instance.

Practical Example

A messaging application might represent a single message as a class instance, making it easy to generate thousands of consistent message objects.

class Message {
  constructor(recipient, sender, body) {
    this.recipient = recipient;
    this.sender = sender;
    this.body = body;
    this.timestamp = new Date(); // Automatically assign a creation time
  }
}

const myMsg = new Message("Alice", "Bob", "Are we still on for lunch?");
console.log(myMsg.timestamp); // Logs the current date/time