Adding and Deleting Object Own Methods

This section provides a quick description of object's own methods. A tutorial example is provided on how to add, call, and delete object's own methods.

When you create a new object from the "Object" constructor, you will get an object with only some default methods:

But you can add more methods to one object at any time using an assignment operation like this:

object_name.method_name = function_name;

The added method is for this one object only. Other objects will not have this method.

Calling a method on an object is the same as calling the assigned function as shown below:

object_name.method_name(param1, param2, ...);

You can also delete methods from one object at any time using a delete operation like this:

delete object_name.method_name;

Here is a tutorial example that shows you how to add a new method, call a method, and delete a method.

<html>
<!-- Object_Method.html
   Copyright (c) 2013 by Dr. Herong Yang, herongyang.com
-->
<head>
<title>Object Methods of "Object"</title>
</head>
<body>
<pre>
<script type="text/javascript">
// My function to say hello
function sayHello(name) {
   window.alert("Hello "+name);
}

   // Preparing two objects of "Object" type
   var mySite = new Object();
   var myBook = new Object();
   mySite.url = "herongyang.com";
   myBook.author = "Herong Yang";

   // Adding a method to one object only
   myBook.greet = sayHello;

   // Calling the method on "myBook"
   myBook.greet(myBook.author);

   // Calling the method on "mySite" - will not work
//   mySite.greet(myBook.author);

   // Deleting the method on "myBook"
   delete myBook.greet;
   
   // Calling the method on the object - will not work
//   myBook.greet(myBook.author);
</script>
</pre>
</body>
</html>

If you run this JavaScript page, you will get alert box on the screen saying: "Hello Herong Yang".

Table of Contents

 About This Book

 Introduction to JavaScript

 ECMAScript Language Specification and JavaScript Dialects

 Data Types, Variables and Expressions

 Flow Control Statements

 Creating, Accessing, and Manipulating Arrays

 Defining and Calling Functions

 Web Browser Supporting JavaScript

 Server-Side and Client-Side Web Scripting

Introduction to Objects

 What Is an Object?

 Objects of "Object" Data Type

 Adding and Deleting Object Own Properties

Adding and Deleting Object Own Methods

 Using "this" Keyword to Represent Current Object

 Object Literals of the "Object" Type

 Objects and Associate Arrays

 Objects with Indexed Properties

 Differences between "Object" and "Array"

 Using "Array" Objects as "Object" Objects

 Defining Your Own Object Types

 Inheritance of Properties and Methods through the Prototype Object Chain

 'jrunscript' - JavaScript Shell Command from JDK

 Using Functions as "Function" Objects

 Introduction to Built-in Object Types

 W3C's Document Object Model (DOM) Specifications

 References

 PDF Printing Version