Creating JavaScript Objects

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Creating JavaScript Objects

With JavaScript, you can define and create your own objects.

There are two different ways to create a new object:

1. Defining and creating an instance of an object
2. Use a function to define an object, and then create a new object instance

Create a direct instance

This example creates a new instance of the object and adds four properties to it:

Instance

Person=new Object ();p erson.firstname= "Bill";p erson.lastname= "Gates";p erson.age=56;person.eyecolor= "Blue";

Try it yourself.

Alternative syntax (using object literals):

Instance

Person={firstname: "John", LastName: "Doe", Age:50,eyecolor: "Blue"};

Try it yourself.

Using the Object Builder

This example uses a function to construct an object:

Instance

function Person (firstname,lastname,age,eyecolor) {this.firstname=firstname;this.lastname=lastname;this.age=age; This.eyecolor=eyecolor;}

Try it yourself.

Creating an instance of a JavaScript object

Once you have the object constructor, you can create a new object instance, just like this:

var myfather=new person ("Bill", "Gates", "page", "Blue"), var mymother=new person ("Steve", "Jobs", "green");

Add attributes to JavaScript objects

You can add a new property to an existing object by assigning a value to the object:

Suppose Personobj already exists-you can add these new properties to it: FirstName, LastName, Age, and Eyecolor:

Person.firstname= "Bill";p erson.lastname= "Gates";p erson.age=56;person.eyecolor= "Blue"; x=person.firstname;

After the above code is executed, the value of X will be:

Bill

Add a method to a JavaScript object

method is simply a function attached to an object.

Methods for defining objects inside the constructor function:

function Person (firstname,lastname,age,eyecolor) {this.firstname=firstname;this.lastname=lastname;this.age=age; This.eyecolor=eyecolor;this.changename=changename;function ChangeName (name) {this.lastname=name;}}

The value of the ChangeName () function name is assigned to the LastName property of the person.

Now you can try it:

Mymother.changename ("Ballmer");

Try it yourself.

JavaScript class

JavaScript is an object-oriented language, but JavaScript does not use classes.

In JavaScript, classes are not created and objects are not created through classes (as in other object-oriented languages).

JavaScript is based on prototype, not class-based.

Creating JavaScript Objects