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

Question

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

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!

node.js
backbone.js
express

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 get Post query in express node.js?

/* 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.
  ...
});