prototype属性可以将属性和方法添加到任何对象(Number, Boolean, String 和Date等)。
注：原型(Prototype)是一个全局的属性，它可以使用在几乎所有的对象。
语法
object.prototype.name = value
实例:
这里有一个例子展示了如何使用原型(prototype)属性的属性添加到对象：
<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>
这将产生以下结果：
Book title is : Perl Book author is : Mohtashim Book price is : 100