Backbone.js model.previous()

The Backbone.js previous model specifies the previous value of the changed attributes.

Syntax:

Parameter explanation:

attributes: It defines the property of a model.

Let's take an example.

See this example:

<!DOCTYPE html>
   <head>
      <title>Model Previous 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>
   </head>
   <body>
   <script type="text/javascript">
      var model = new Backbone.Model({
         jersey:10,
         player:'Dhoni'
      });
      model.set('jersey', '99');
      document.write("Value of jersey after set: ", JSON.stringify(model.changedAttributes()));
      document.write("<br>");
      document.write("The previous value of jersey is: ", model.previous('jersey'));
   </script>
   </body>
</html>

Test it Now

Output:

Save the above code in previous.html file and open this file in a new browser.