JavaScript Objects

Hi everyone, Today we are going to discuss about objects of JavaScript.
JavaScript is an object based programming language. So, everything in JavaScript is an object. A JavaScript object is an entity which have properties and methods.

There are 3 ways to create objects in JavaScript. Let's look at these methods one by one with examples.

1. By object literal
2. By creating instance of object
3. By using a constructor

By object literal

Syntax

object_name = {property1 : value1 , property2 : value2, ...}

Let's look at an example and try to understand it. 

Example 1

Figure 1

In here, we create an object named 'employee'. There are 3 properties for this object, they are id, name and age. We assign values for each of this property. To access the property of object we must use, 

object_name.property

Try to access by simply using property without object name will not be work. You can try it and watch the result.

Here is the result we got.

Figure 2

In the result, id, name and age of employee is shown.

By creating instance of object

In here, we create an object using new keyword.

Syntax

var object_name = new Object();

Example 2

Figure 3

In here, we first declared an object. Then we add properties to object as 

                                               object_name.property = property value 

Here is the result.

Figure 4

As you can see, we got the same result as previous example.

By using a constructor

First we look at what constructor is. A constructor is a special method of a class or structure in object-oriented programming that initializes an object of that type. It can be used to set the values of the members of an object, either to default or to user-defined values. JavaScript provides a special constructor function called Object() to build the object.

In here, we create a function with arguments, each argument value can be assigned in the current object by using 'this' keyword. In here, this keyword refers to the current object.

Syntax

function object_name(parameter1, parameter2){

this.parameter1 = parameter1;

this.parameter2 = parameter2;

}

Let's look at the example and try to figure it out.

Example 3

Figure 5

In here, we create a function called 'employee' and properties are included as parameters of function. The result we got is same as previous examples.

Figure 6

Defining methods of an object

To do this, we have to add property in the function with same name as method.

Example 4

Figure 7

In here we add a property called changeAge in function 'employee'. Also there is a method in same name. We can change age by using changeAge method. We can do it as follows.

object_name.property(property_value);

So, in our example, it is as follows.

emp.changeAge(35);

Figure 8 shows the output we got.

Figure 8

Hope you'll get a better understand about objects. Thank you for watching this tutorial.