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So, you want to do a partial update to a model in backbone.js, that is call Backbone.Model.save(). But .save(), by default saves back the entire model.

So, you can specify a partial update in the optional parameters:

model.save({}, { data: JSON.stringify(myPartialUpdate), contentType: 'application/json', ...}

Backbone.Model.save() calls Backbone.sync() which invokes JQuery's ajax().

If you put the partial update and the content type header in the options, then Backbone.sync() will put those into the parameters object that's passed to JQuery.ajax.

Of course, one could just provide your own implementation of .sync() in your model since .save() looks for that before delegating to Backbone.sync().
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