Extra fields in model

Question

im using Backbone.js to manage models and collections in my app. So, i have a "Usuario" model that match with a user entity in the database. This is the code:

var Usuario = Backbone.Model.extend({
   defaults:{
      idusuario: 'undefined',
      apellido: 'undefined',
      nombre: 'undefined',
      dni: 'undefined',
      dom_usuario: 'undefined',
      nombreusuario: 'undefined',
      activo: 'undefined',
      bloqueado: 'undefined',
      recomendar_cambio_clave: 'undefined',
      isChecked: false
   }
});

All fields of the model are in the entity user, except "isChecked".The isChecked attribute, will be true when the user model is checcked. But when i query by "isChecked" js not recognize the variable:

console.log(this.model.get('isChecked')); 
undefined
console.log(this.model.get('nombre')); 
Horacio José

Any ideas ?.

UPDATE 1 It is a extract of my code, where load the collection (of Usuario) via Ajax:

var anUrl = $("#ajax-call").val();
var myCol = new CustomCollection({
    model: Usuario,
    filterAttribute: 'apellido'
});

myCol.fetch({async: false, url: anUrl});
myCol.saveOriginal();
console.log(myCol);

When, show in console the collection, the models not contains "isChecked" property:

Answer 1

With the details you've provided it's hard to know if the error is in your view's initialization or anything else. Using this fiddle you can see your example works perfectly. I created a view in that fiddle trying to mimic your scenario.

However, don't confuse 'undefined' or "undefined" with undefined. "undefined" == undefined and "undefined" === undefined are both false.

So, your model should be:

var Usuario = Backbone.Model.extend({
   defaults : {
      idusuario : undefined,
      apellido : undefined,
      nombre : undefined,
      dni : undefined,
      dom_usuario : undefined,
      nombreusuario : undefined,
      activo : undefined,
      bloqueado : undefined,
      recomendar_cambio_clave : undefined,
      isChecked : false
   }
});

And then:

var u = new Usuario();
console.log(u.get("isChecked"));

Should give your expected result.

Answer 2

I solve mi problem. I create dynamically the property "isChecked", querying is the value is defined or not:

toggleModel: function(){
    var current = this.model.get('isChecked');
    var status =  current === undefined ? true : !current; 
    this.model.set('isChecked',status);
}

Thanks @Meta for the reply.