Backbone.js/express.js parameters for model.save() - node.js

Question

I'm using Backbone.js on the client and node.js on the backend, and I'm having a bit of trouble doing a 'limited' model save, as explained here : http://backbonejs.org/#Model-save
As in the example, if I do
book.save({author: "Teddy"});
how do I access the parameters of the save using express.js, i.e. the fact that I only want to save to the 'author' field? I've tried the following
req.body -> gives ALL parameters of the model being saved, I want only the 'author' field
req.query -> empty
Any help much appreciated!

Answer 1

As stated in Model.save documentation:
save model.save([attributes], [options])
[...] The attributes hash (as in set) should contain the attributes you'd like to change —
keys that aren't mentioned won't be altered — but, a complete
representation of the resource will be sent to the server.
You can however override the save method and provide a data attribute via the options which will be sent to the server instead of the full model representation. For example, this will only save the attributes passed to the method :
var M = Backbone.Model.extend({
save: function (attrs, options) {
options || (options = {});
options.contentType = 'application/json';
options.data = JSON.stringify(attrs);
Backbone.Model.prototype.save.call(this, attrs, options);
}
});
And a Fiddle http://jsfiddle.net/dLFgD/
As #mikebridge noted in the comments, this behavior can now be obtained by passing an attrs option. So either use
book.save(null, {
attrs: {author: "Teddy"}
});
or keep the override
var M = Backbone.Model.extend({
url: '/echo/json/',
save: function(attrs, options) {
options || (options = {});
options.attrs = attrs;
Backbone.Model.prototype.save.call(this, attrs, options);
}
});
http://jsfiddle.net/nikoshr/dLFgD/7/
You could also send a PATCH request if you're using a Backbone version that supports it (>=0.9.9) and your server understands that verb, as explained in #pkyeck's answer

Answer 2

with the current version of Backbone (1.1.0) you could also do a PATCH which only sends the changed attributes to the server.
If instead, you'd only like the changed attributes to be sent to the server, call model.save(attrs, {patch: true}). You'll get an HTTP PATCH request to the server with just the passed-in attributes.
taken from here: http://backbonejs.org/#Model-save
in your case this would be:
book.save("author", "Teddy", {patch: true});

Answer 3

The best way I have found to access POST parameters is to use the bodyParser middleware. This is referenced at this question: How to retrieve POST query parameters?
/* On startup, register the bodyParser middleware */
app.use(express.bodyParser());
/* Then, during route execution, each parameter can be accessed with req.param */
app.post('/author/:id', function(req, res) {
var author = req.param('author', null); // Second parameter is default.
...
});