Classes & Constructors

JavaScript classes provide a clear, concise syntax to create objects and manage inheritance. They act as blueprints for objects, defining properties and behaviors.

What is a Class?

A class is a template for creating objects. It encapsulates data (properties) and functions (methods) that operate on that data.

Constructor Method

The constructor is a special method inside a class. It runs automatically when you create a new instance, setting initial property values.

Creating a Class with a Constructor

Here’s the simplest way to create a class with a constructor that initializes properties:

class Car {
  constructor(make, model) {
    this.make = make;   // Property 'make' initialized
    this.model = model; // Property 'model' initialized
  }
}

Instantiating Objects

Use the new keyword to create an instance of the class and pass arguments to the constructor:

const myCar = new Car('Toyota', 'Corolla');
console.log(myCar.make);  // Output: Toyota
console.log(myCar.model); // Output: Corolla

Key Points About Classes & Constructors

• Classes are syntactic sugar over JavaScript's prototype-based inheritance.
• The constructor method initializes new objects.
• If no constructor is defined, a default empty constructor is used.
• Use this to assign properties inside the constructor.

Adding Methods to a Class

Methods can be declared inside the class but outside the constructor. They become part of the object's prototype.

class Car {
  constructor(make, model) {
    this.make = make;
    this.model = model;
  }
  getDescription() {
    return `${this.make} ${this.model}`;
  }
}

const myCar = new Car('Honda', 'Civic');
console.log(myCar.getDescription()); // Honda Civic