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

Its syntax is as follows −

object.prototype.name = value

Example

Try the following example.

Live Demo

<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>

Output

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

javascript_number_object.htm