Simple fsm

fsm.js

var fsm = (function() {
    function transition(name, from, to) {
        this.transitions[name] = {name: name, from: from, to: to};
        return this;
    }

    function init(state) {
        this.initState = state;
        return this;
    }

    function isTransitionAllowed(transition, state) {
        var from = transition.from;
        return from === state || from === '*';
    }

    function camelize(string) {
        return string.slice(0, 1).toUpperCase() + string.slice(1);
    }


    return function() {
        function fsm(name, target) {
            target = target || this;
            var state = target.__state || fsm.initState;
            var transition = fsm.transitions[name];

            if (!transition) {
                throw new Error('No such transition');
            }

            if (!isTransitionAllowed(transition, state)) {
                throw new Error('Transition is prohibited');
            }

            target.__state = transition.to;
            target['onState' + camelize(transition.to)](transition);

        }

        fsm.transitions = {};
        fsm.initState = null;

        fsm.transition = transition;
        fsm.init = init;

        return fsm;
    };

})();

var lampController = fsm()
    .init('off')
    .transition('enable', 'off', 'on')
    .transition('disable', 'on', 'off');


var lamp = {
    controller: lampController,
    onStateOff: function() {
        console.log('OFF');
    },
    onStateOn: function() {
        console.log('ON');
    }
};

lamp.controller('enable');
lamp.controller('disable');