BackboneJS-Model isValid

BackboneJS-Model isValid

<!DOCTYPE html>
   <head>
      <title> Model Example</title>
         <script src="https://code.jquery.com/jquery-2.1.3.min.js" type="text/javascript"></script>
         <script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.2/underscore-min.js" type="text/javascript"></script>
         <script src="https://cdnjs.cloudflare.com/ajax/libs/backbone.js/1.1.2/backbone-min.js" type="text/javascript"></script>
         <script type="text/javascript">
            var Person = Backbone.Model.extend({
               defaults: {
                  name: '',
                  age: 25,
               },
            validate: function(attributes) {
               if (attributes.name == '') {
               document.write("please enter the name!!!!");
               }
            }
            });
            var person = new Person({
               name: 'John'
            });
            document.write("The passed value for attribute 'name' is: ", person.isValid());

         </script>
   </head>
   <body></body>
</html>