prototype
描述 (Description)
prototype属性允许您向任何对象添加属性和方法（Number，Boolean，String和Date等）。
Note - Prototype是一个全局属性，几乎可用于所有对象。
语法 (Syntax)
使用以下语法来使用Prototype。
object.prototype.name = value
例子 (Example)
请尝试以下示例以使用prototype属性向对象添加属性。
<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>
输出 (Output)
Book title is : Perl
Book author is : Mohtashim
Book price is : 100
