The prototype attribute can add properties and methods to any object (Number, Boolean, String and Date, etc.).
Note: Prototype is a global property that can be used in almost all objects.
Grammar
object.prototype.name = value
Example:
Here is an example showing how to add properties to an object using the prototype attribute:
<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 the following results:
Book title is : Perl Book author is : Mohtashim Book price is : 100
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