JavaScript Inheritance

Prototype-based Inheritance:

• JavaScript uses prototype-based inheritance where objects inherit properties and methods from prototypes.

Prototype Chain:

• Objects in JavaScript have a hidden [[Prototype]] property, which refers to another object. This forms a chain of prototypes, known as the prototype chain.

Example: Creating a Parent Object

function Shape(color) {
  this.color = color;
}
Shape.prototype.getColor = function() {
  return this.color;
};

Creating a Child Object (Inheriting from Parent)

function Circle(radius, color) {
  Shape.call(this, color); // Call the parent constructor
  this.radius = radius;
}
Circle.prototype = Object.create(Shape.prototype); // Inherit from Shape
Circle.prototype.constructor = Circle; // Reset the constructor
Circle.prototype.getRadius = function() {
  return this.radius;
};

Instanceof Operator:

• The instanceof operator tests whether an object has in its prototype chain the prototype property of a constructor.

Example: Using Instanceof

const circle = new Circle(5, 'red');
console.log(circle instanceof Circle); // Output: true
console.log(circle instanceof Shape); // Output: true

 

Key Points

• JavaScript inheritance is based on the prototype chain, where objects inherit properties and methods from their prototypes.
• Constructors and prototypes are used to establish inheritance relationships between objects.
• Inheritance in JavaScript allows for code reuse and the creation of hierarchies of related objects.