ex-machina

A minimalist state machine.

Installation

It is available with bower or npm:

bower install ex-machina
npm install ex-machina

Include ex-machina.min.js to the HTML, and the exMachina object is now available in the global scope:

<script type="text/javascript" src="/path/to/bower_components/ex-machina/dist/ex-machina.min.js"></script>

Alternately, you can use Browserify or RequireJS to avoid global scoping.

var exMachina = require('ex-machina');

Usage

Create a state machine

To create a state machine, use the exMachina factory:

var machine = exMachina({
    state1: {
        state2: function(payload) {
            return <condition>;
        }
    }
})

You must pass a config object to the state machine factory. It describes all available transitions. In the above example, when state1 is ended, if the given callback for state2 returns true, the state2 will be activated. The payload is the value returned by the state which is state1 here.

Note: Only one state can be activated at the same time.

Add a state

When your state machine is created, you must register all states you described into your config object:

machine.state('state1', function(payload) {
    // the payload is the value returned by the previous state or 
    // the initial payload if it is the first state
    
    // you can return a payload.
    // if you perform asynchronous operation, return the promise.
    // The payload will be the result of the promise
    return <new_payload>;
});

Run the state machine

To run your state machine, just execute it:

machine('<initial_state>', '<initial_payload>')
    .then(function(payload) {
        // a final state was reached
    }, function(error) {
        // an error occurred
    });

Dealing with events

The state machine triggers some events before and after state activation:

machine.on(machine.PRE_STATE_EVENT, function(data) {
    // this is triggered before a state activation
    // data looks like { stateName: <something>, payload: <something> }
});

machine.on(machine.POST_STATE_EVENT, function(data) {
    // this is triggered after a state activation
    // data looks like { stateName: <something>, payload: <something> }
});

Development

Install dependencies:

make install

Build

To rebuild the minified JavaScript you must run: make build.

During development you can run make watch to trigger a build at each change.

Tests

make test

Contributing

All contributions are welcome and must pass the tests. If you add a new feature, please write tests for it.

License

This application is available under the MIT License.