var ContactModel = Backbone.Model.extend({ //extend Backbone.Model defaults: { firstName : 'no first name yet', lastName : 'no last name yet' } }); var contact1Model = new ContactModel( //instantiate model instance {firstName:'John'} ); // firstName is set to John while lastname remains the default value console.log(contact1Model.get('firstName')); //logs John console.log(contact1Model.get('lastName')); //logs 'no last name yet'