Backbone.js finite state machine view

I developed a basic Backbone.js finite state machine (FSM) view for use on a project I was working on a while ago, and have been meaning to clean up the code and share it for a while now. It is now available on github, along with some qunit and sinon tests.

It was written to handle complex form navigation, i.e. when you want to conditionally guide a user through a path of form fields depending on their previous answers, and so while it could perhaps be shoehorned into other uses, this is where it will be the most natural fit. It works basically by binding a method to the change event on form fields that translates this event into terms understood by the FSM, and then calls transitions that you’ve defined when initializing the view.

There is some basic js and HTML on the github page demonstrating use. I plan to have more/better code, along with a working example, at some point.

backbone-fsm-view

Since writing this a few other people have come up with implementations that, though they appear quite different from mine, would accomplish mostly the same thing. See backbone.statemachine, and machina.js. Also, I definitely got inspiration for this code from a few other places on the web while writing it, but can’t track them down now. If anyone reading this thinks it reminds them of something they’ve seen elsewhere, or if they have suggestions on how it could be improved, feel free to let me know. I’m always open to suggestions and/or pull requests.

Closure compiler externs files for underscore and backbone js

As part of some other things I’m working on I’ve begun building upon some existing closure compiler externs files for the Underscore and Backbone js libraries. Both are still in quite early stages, but if you need something like this, they’re currently better than nothing.

backbone-js-externs on github, for Backbone 0.9.2

underscore-js-externs on github, for Underscore 1.3.3

The Backbone externs file is taken from this gist, which was autogenerated by DotNetWise’s externs extractor. It does a decent but very basic job.

The Underscore externs file is taken from the official Closure Compiler repository. The only changes I’ve made so far are

  • fixing a type annotation for the _.uniq and _.unique functions that had a required parameter after a non-required one (Closure Compiler dislikes this)
  • using same type annotation for _.uniq and _.unique, since the latter is an alias for the former
  • beginning to add type annotations for functional-style usage of underscore, vs. object notation (e.g. _(collection).map(function(){}) vs. _.map(collection, function() {}). The existing externs file has only the latter.

I’ll probably also be adding externs for use with the SVG library Raphael at some point.

Cisco IPsec VPN on OSX Snow Leopard

For anyone else having issues setting up a VPN connection on Snow Leopard: if you are getting an “incorrect shared secret” error, quit wasting your time, and download Shimo, a VPN client for OSX. Haven’t paid for it yet, but will likely end up doing so, since it’s the only one of a half-dozen or so that I tried that not only worked, but wasn’t horribly designed.

I suspect my issue may have been related to a the VPN shared secret being too long, though that is mostly speculation. There was mention in a forum somewhere that OSX Lion silently truncates shared secret keys longer than 63 characters. Yay.

Errors in scripts loaded with jQuery $.getScript

Spent some time the other day trying to figure out why I wasn’t seeing JavaScript errors in certain files where I expected to, which was problematic both for development and also for the monitoring of client-side errors we’re doing in the application (assigning a handler to window.onerror that makes an ajax call with error information to an endpoint for this purpose).

Basically, if there are errors in any of the scripts you are loading with $.getScript, or the full $.ajax call for which $.getScript is shorthand, these will be caught by jQuery and will fail to show up in the console or be passed to any window.onerror handler you’ve defined. jQuery provides a global ajaxHandler you can attach to, for example, document, which you can then use to do whatever client-side error handling/logging you want to do.

The downside of this approach is (as far as I can tell) that you don’t get quite as much error information (specifically, the line number of the error) from jQuery as you do from other ways of loading scripts with js, because the error gets caught during a call to eval (or more specifically, jQuery’s globalEval method).

Objects in closure compiler record types

I’ve been diving much deeper into closure compiler’s type checking abilities lately, and while it is a great tool, the documentation could stand to be improved somewhat.

Sometimes when creating a record type, you will want to specify not just that some property is an array, or an object, but what sort of things are in the array, or what sort of properties are on the object.

A simple record type for an object with a string and number property:


/**
 * @typedef {{name: string, index: number}}
 */

A record type with an array of strings:


/**
 * @typedef {{networks: Array.<string>}}
 */

A record type, one of whose properties is an object:


/**
 * @typedef {{authorized:boolean, network_name: string,
 * details: Object.<{id: number, promotion_id: number}>, type: string}}
 */

 

This last one is the syntax I was having trouble coming up with, and it is not immediately obvious from the official documentation here. Hope this might help someone else who’s looking for the same thing.

Also, an example of objects inside an array (using this for a Vimeo video object):


/**
 * @typedef {{urls: {url: Array.<Object.<{type: string, _content: string}>>},
 * thumbnails: {thumbnail: Array.<Object.<{_content: string, width: string, height: string}>>} }}
 * }}
 */

 

You can also refer to other record types inside a record type:


/**
 * @typedef {{name: string, auth_provider: string, id: number}}
 */
MyRecordTypes.authorization;

/**
 * @typedef {{authorizations: Array.<MyRecordTypes.authorization> }}
 */
MyRecordTypes.authorizations;

Automatic brain, free person

I agree with much of what Michael Gazzaniga says here, and with the overall thrust of the project exemplified most recently in his book Who’s in Charge?: Free Will and the Science of the Brain.

However, as much as we might like to make this project entirely palatable, there is an important sense in which it does seem to challenge some stubborn intuitions, and I think we need to recognize the fact that such findings can and do influence our ideas about how and when to hold people responsible. The clearest evidence for this is found in the legal realm where, from the insanity defence to the twinky defence, we encounter a long history of attempts to grapple with the relation between the apparently mechanistic nature of the brain and our ability to hold people responsible for their actions–attempts which clearly show that a scientific-mechanistic understanding of the brain has important bearing on our understanding of freedom and agency.