1、描述
prototype属性允许为任何对象（Number, Boolean, String 和 Date等）添加属性和方法。
注意：prototype是一个全局属性，几乎所有的对象都可用。
2、语法
它的语法如下：
object.prototype.name = value3、例如
<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("C#", "cjavapy");
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>