How to prevent a javascript/backbone.js cloned model from sharing attributes

I'm working with backbone.js models, so I don't know if my question is particular to the way backbone handles cloning or if it applies to javascript in general. Basically, I need to clone a model which has an attri开发者_如何转开发bute property assigned an object. The problem is that when I update the parent or clone's attribute, the other model is also updated. Here is a quick example:

var A = Backbone.Model.extend({});
var a = new A({'test': {'some': 'crap'}});
var b = a.clone();

a.get('test')['some'] = 'thing';
// I could also use a.set() to set the attribute with the same result

console.log(JSON.stringify(a))
console.log(JSON.stringify(b))

which logs the following:

{"test":{"some":"thing"}}
{"test":{"some":"thing"}}

I would prefer to clone a such that b won't be referencing any of its attributes. Any help would be appreciated.

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Backdone does not do a deep-clone, but only clone first level attributes. You have to clone the values yourself (when it is a hash or array for exemple).

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You could do

var A = Backbone.Model.extend({});
var a = new A({'test': {'some': 'stuff'}});
var b = new A(a.model.toJSON());

Adapted from this answer: How to clone a backbone collection

---

var A = Backbone.Model.extend({});
var a = new A({'test': {'some': 'stuff'}});
var b = a.clone();

b.attributes = $.extend(true, {}, b.attributes);

// try to overwrite "some" without affecting "a" model
var someStuff = {'test': {'some' : 'other stuff'}};
b.set(someStuff);

console.log(a.toJSON());
console.log(b.toJSON());

http://jsfiddle.net/RLWzm/