Object Oriented Programming in JavaScript

Introduction

JavaScript is a prototype-based programming style of object-oriented programming in which classes are not present.

It can support OOP because it supports inheritance through prototyping as well as properties and methods.

Object Oriented Programming in JavaScript is known as prototype-based programming.

1. Creating Class in JavaScript 
   the following syntax is used for declaring a class in JavaScript:
   
   1. function Emp() {  
   2.     alert('Emp instantiated');  
   3. }  
   Here Emp can act as a class in JavaScript. 
   
   The body of Emp acts as a constructor and is called as soon as we create an object of the class.
    
2. Creating Objects of Emp Class
   Using the following syntax we can create an object of the Emp class:
   
   1. var Emp1 = new Emp();  
   As soon as we create an object of the Emp class the constructor will be called.
   
   Here the above function Emp would be treated as a class in JavaScript

2.Running the code

An alert will be shown on the page load of the web form.

3. Properties of class
We can define the properties of a class in the following way:

1. function Emp(firstname) {  
2.     alert('Emp instantiated');  
3.     this.firstname = firstname;  
4. }  

• Passing value to properties
  
  1. var Emp1 = new Emp("Devesh is Emp of GENPACT INDIA");  
  2. alert(Emp1.firstname); 
• Snap for defining properties

Sample code

var Emp1 = new Emp("Devesh is Emp of GENPACT INDIA"); 

Advance Javascript 

JavaScript is a prototype-based programming style of object-oriented programming in which classes are not present.

It can support OOP because it supports inheritance through prototyping as well as properties and methods.

Object Oriented Programming in JavaScript is known as prototype-based programming.

Now we will learn methods in JavaScript classes.

Use the following procedure to create a sample to help understand how to create methods in JavaScript classes.

1. Creating Class in JavaScript
   The following syntax is used for declaring a class in JavaScript:
   
   1. function Emp(NAME) {  
   2.     alert("EMP Instantiated");  
   3.     this.NAME = NAME;  
   4. }  
   Here Emp can be act as a class in JavaScript and this.NAME would act as a property.
   
   The body of Emp acts as the constructor and is called as soon as we create an object of the class

Calling functions

1. var Emp1 = new Emp('DEVESH');  
2. var Emp2 = new Emp('ROLI');  
3.   
4. Emp1.Fun1();  
5. Emp2.Fun1()  
6. }  

Here we created two instances of EMP, EMP1 and EMP2 and passed a parameter to the constructor to assign a NAME Property.

Using EMP1.Fun1() and EMP2.Fun1() we are calling the functions.

We have defined an alert inside this function:

Running the code
After running the code we will get two alerts, each for EMP1.fun1() and Emp2.Fun1();

1. Other ways to create JavaScript objects
   
   We can create an object in JavaScript in the following way also:
   
   1. var EMP = {  
   2.     firstName:"ROLI",  
   3.     lastName:"GUPTA",  
   4.     age:28,  
   5.     sex:"F"  
   6. };  
2. Accessing EMP objects

1. 1. alert("EMP NAME: " + EMP.firstName + " " + EMP.lastName + " EMP AGE: " + EMP.age + " EMP SEX : " + EMP.sex);
   Complete Code
   
   1. var EMP = {  
   2.    firstName: "ROLI",  
   3.    lastName: "GUPTA",  
   4.    age: 28,  
   5.    sex: "F"  
   6. };  
   7. alert("EMP NAME: " + EMP.firstName + " " + EMP.lastName + " EMP AGE: " + EMP.age + " EMP SEX : " + EMP.sex); 
2. Running the code

Defining Methods

1. var EMP = {  
2. firstName: "ROLI",  
3. lastName: "GUPTA",  
4. age: 28,  
5. sex: "F",  
6. fullName: function () { return this.firstName + " " + this.lastName }  
7. };  
8. alert("Full name is: "+EMP.fullName());  

We have defined the fullName method inside the EMP class.

It returns the join of fname and lname.

Running the code