I’ve released a new version, 0.2.2, of the JavaScript FSM builder. There are some enhancements, such as accessors for successorStates and expectedEvents that I found useful for implementing a first (almost) practical example involving drag & drop.

Speaking of which, this whole thing didn’t come into being because of a pressing need. Currently, it’s more of a solution looking for a problem. I know that state machines can be very helpful for UI construction, however, this particular incarnation still has to prove itself.

All the rest

• Just the script
• The specs (Look at the source)
• The complete package

I like finite state machines and I wanted to try metaprogramming in JavaScript ever since I’d seen Adam McCrea presentation on the topic.

The result is an FSM builder in JavaScript. Machine descriptions look like my test machine here:

var Machine = FSM.build(function(fsm) { with (fsm) {
  onUnexpectedEvent(function() { ... });

  state('start', 'initial')
    .event('go')
      .goesTo('middle')
      .doing(function() { ... })
      .doing('phew')
    .event('run')
      .goesTo('finish')
    .onExiting(function() { ... });

  state('middle')
    .onUnexpectedEvent(function() { ... })
    .onEntering(function() { ... })
    .event('back')
      .goesTo('start')
      .onlyIf(function() { return true_or_false })
    .event('go')
      .goesTo('finish');

  state('finish', 'final');
}});

function TestMachine() {}
// amend TestMachine.prototype here all the way you want
TestMachine.prototype.phew = function() { ... };
TestMachine.prototype = new Machine(TestMachine.prototype);

There’s no documentation yet, but thorough unit testsspecs
using Nicolás Sanguinetti’s very nice js-spec framework.

Something to look at:

• Just the script
• The specs (Look at the source)
• The complete package

The script is meant to be usable independently of and play nicely with any other libraries.

The manner in which an FSM is attached to classes/objects is still rather convoluted. The general idea is that it (a) should be possible to insert the FSM as the first link in the prototype chain and (b) should be possible to directly attach it to an existing object. I’d appreciate suggestions how to make this nice and shiny.