JavaScript toSource方法

<html>
   <head>
      <title>JavaScript toSource() Method</title>
   </head>

   <body>

      <script type = "text/javascript">
         function book(title, publisher, price) {
            this.title = title;
            this.publisher = publisher;
            this.price = price;
         }

         var newBook = new book("Perl","Leo Inc",200);
         document.write(newBook.toSource());
      </script>

   </body>
</html>