JavaScript is one of the most popular languages used by programmers all around the world. In this course, you'll be introduced to the Object-Oriented Paradigm of JavaScript. The course will discuss OOP in both, ES5 and ES6 versions of JavaScript. It begins with a basic introduction to what Object-Oriented programming is, followed by its comparison to other languages. It then introduces the new  OOP features available in ES6 version and compares it to the ES5 version. The course then discusses objects in JavaScript followed by the use of function as objects in OOP. It goes over the interesting concepts of prototype objects, data encapsulation, and classes. It then delves into the more complex concepts of inheritance in both the versions, including prototypal inheritance, prototype chaining, method overriding and mixins. The course is filled with interesting illustrations to help in your understanding of the concepts as well as numerous quizzes and exercises to help you practice.

Learn Object-Oriented Programming in JavaScript

## Defining Methods

Methods are defined differently in the *constructor* functions.

### Example
We defined our methods inside the object literals in the following way:

//creating an object named employee
var employee = {
  //defining properties of the object
  //setting data values
  name : 'Joe',
  age : 28,
  designation : 'Developer',
  //function to display name of the employee
  displayName() {
    console.log("Name is:", this.name)
  }
}
//calling the method
employee.displayName()

Now, let's write the same function but for the constructor function this time:

//creating an object named Employee
function Employee(_name,_age,_designation) {
   this.name = _name,
   this.age = _age,
   this.designation = _designation,
  //function to display name of the Employee
  this.displayName = function() {
    console.log("Name is:", this.name)
  }
}
//creating an object
var employeeObj = new Employee('Joe',22,'Developer')
//calling the method for employeeObj
employeeObj.displayName()

#### Explanation
In **line 9** of the code for object literal, the method declaration was simple; the name of the function followed by the definition, i.e., the body of the function. 

However, as seen in **line 7** of the *constructor* function code, in order to define the method, `this` keyword is used. As discussed earlier, `this` is used to set as well as assign the method and properties to every new object that is created.

>**Note:** The `function` *keyword* provides another way to declare a function. It can be used while declaring a function in an object literal as well.

## Adding a Method

Just like adding *properties*, adding a *method* to a *constructor* function is different than adding it to an object. 

Let's compare the two methods.

### Example
A new method is added to an object in the following way:

# Defining Methods

Methods are defined differently in the *constructor* functions.

## Example
We defined our methods inside the object literals in the following way:

### Explanation
In **line 9** of the code for object literal, the method declaration was simple; the name of the function followed by the definition, i.e., the body of the function. 

However, as seen in **line 7** of the *constructor* function code, in order to define the method, `this` keyword is used. As discussed earlier, `this` is used to set as well as assign the method and properties to every new object that is created.

>**Note:** The `function` *keyword* provides another way to declare a function. It can be used while declaring a function in an object literal as well.

# Adding a Method

Just like adding *properties*, adding a *method* to a *constructor* function is different than adding it to an object. 

Let's compare the two methods.

## Example
A new method is added to an object in the following way:

This lesson teaches how to define and add new methods in a constructor function.

Methods in Constructor Functions

Defining Methods

Example

Explanation