Model.set() with new and undefined values

http://stackoverflow.com/questions/15350864/model-set-with-new-and-undefined-values-in-backbone-js

HTML

<script src="//cdnjs.cloudflare.com/ajax/libs/lodash.js/1.0.1/lodash.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/backbone.js/0.9.10/backbone-min.js"></script>
<a href="http://stackoverflow.com/questions/15350864/model-set-with-new-and-undefined-values-in-backbone-js">Stack Overflow Question</a>

JavaScript

// Currently
var k ="hello";
var m = new Backbone.Model({ "foo": "bar" });
m.set({"baz": "bar", "foo": k});
console.log(m.changedAttributes()); // { "baz": "bar", "foo": undefined }
console.log(m.attributes); // {foo: undefined, baz: "bar"}