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# Javascript Object - prototype

## Description:

The prototype property allows you to add properties and methods to any object (Number, Boolean, String and Date etc).

Note: Prototype is a global property which is available with almost all the objects.

## Syntax:

    object.prototype.name = value

## Example:

Here is an example showing how to use the prototype property to add a property to an object:

    <html>
    <head>
    <title>User-defined objects</title>

    <script type="text/javascript">

    function book(title, author){
        this.title = title;
        this.author  = author;
    }
    </script>
    </head>
    <body>
    <script type="text/javascript">
       var myBook = new book("Perl", "Mohtashim");
       book.prototype.price = null;
       myBook.price = 100;
       document.write("Book title is : " + myBook.title + "<br>");
       document.write("Book author is : " + myBook.author + "<br>");
       document.write("Book price is : " + myBook.price + "<br>");
    </script>
    </body>
    </html>

This will produce following result:

    Book title is : Perl
    Book author is : Mohtashim
    Book price is : 100

To understand it in better way you can Try it yourself.

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