Question

Backbone.js has a neat feature where you are able to sync changes back to your sever using standard HTTP verbs.

For example you may have a model object and some code which executes a get:

var coolModel = Backbone.Model.extend({url:'mysite/mymodel'});
var myCoolModel = new coolModel();
myCoolModel.fetch({error:processError});

Under the case where the server returns a 4XX or 5XX the error function ‘processError’ is run, which is great, you are able to process the error in which ever way suits.

As backbone.js uses jQuery to perform the GET, Jquery reports the error, which it is. The 4XX is a valid error which should be recovered from, my client side app is not broken, it just needs to behave slightly differently.

My question is – is it considered bad practice to have this error raised from jQuery displayed in the browsers console window or status bar? Should I be suppressing this error somehow so that users in production don’t see an error reported by the browser when the error is recoverable? Or is it correct in the land of HTTP to leave it as is?

Answer 1

Handling errors in Backbone is a really interesting topic and one I hope to write about at some point. It’s very nice to visually indicate errors to your users in a non-obtrusive manner. Some things to consider are:

• Your users are not looking at the status bar or developer tools
• Your users are expecting specific behavior from your application
• When your application does not behave correctly visual problem indicators are important

I’d recommend considering how the failure impacts the user’s intention. For instance if they are fetching data for the first page and that data is not returned correctly, you will need to handle the error by displaying a failure of data retrieved (or even better fall back on previously loaded data from a cache… it it exists). If the intention is to save an item and the error code returned is 400 that is definitely not a success and should be indicated that the user should retry saving again, (or perhaps attempt a re-save on an interval).

You can silently ignore errors and not indicate them, but your users will get confused and it will lead to unexpected problems. I can’t preach to use perfect error handling, because I’m still getting better at it myself.