Object Oriented JavaScript

This blog explores object oriented programming in JavaScript.

Introduction

 

JavaScript is a prototype-based programming language, which has no class as C++, C#, Java etc. JavaScript uses functions as the classes.

You can define a private or local variable inside a class by using var keyword. When you define a variable without var keyword inside a class, it acts as a public variable.

 

Prototype-based programming is a style of an object-oriented programming in which classes are not present and code re-usability or inheritance is achieved by decorating existing objects, which acts as prototypes. This programming style is also known as class-less, prototype-oriented or instance-based programming.

var ClassA = function() {
    this.Name = "tanuj";
};
var a = new ClassA(); // object creation
ClassA.prototype.print = function() { // further Add Any thing in object on the fly.
    console.log(this.Name);
};
var inheritfrom = function(child, parent) { // Generic function for Any inheritance
    child.prototype = Object.create(parent.prototype) // cloneing the protitype
};
var ClassB = function() // Class 2
{
    this.name = "in Class 2";
    this.surname = "i am child";
    console.log(this.surname + this.name);
};
inheritfrom(ClassB, ClassA); // Actual inheritance
a.print(); // function call from class
var b = new ClassB(); // object creation
b.print(); // calling base class function from child object
// overriding the print function of Class B
ClassB.prototype.print = function() {
    ClassA.prototype.print.call(this); // overloading
    console.log("B callong overload");
};
b.print();
/// Class C inheritance
var ClassC = function() { // Class C
    this.name = "Class C name";
    this.surname = "Class C Surname";
};
inheritfrom(ClassC, ClassB);
ClassC.prototype.foo = function() {
    console.log("in class C foo");
};
ClassC.prototype.print = function() { // overriding
    ClassB.prototype.print.call(this);
    console.log("overriding in Class C");
};
var C = new ClassC();
C.print();