JS State Machine

Machine.js

function Machine() {
	this.states = [];
	this.current = null;
	this.verbose = false;
}
	Machine.prototype.advance = function (input) {
		function next(pass) {
			this.current = this.states.filter(function (state) {
				return state.name === this.current.to
			}, this).pop();
			this.advance(pass);
		};
	
		if (this.verbose)
			console.log((this.current.to ? 'doing:' : 'finally:'), this.current.name);
	
		this.current.action.call(this, input, next.bind(this));
	
	};
	
	Machine.prototype.define = function (states) {
		this.states = this.states.concat(states);
		return this;
	};
	
	Machine.prototype.add = function (states) {
		states = [].concat(states);
		states.forEach(function (state) {
			var index;
			this.states = this.states.map(function (st, ind) {
				if (st.to === state.before) {
					st.to = state.name;
					index = ind;
					state.to = state.before;
				}
				return st;
			});
			delete state.before;
			this.states.splice(index, 0, state);
		}, this);
		return this;
	}
	
	Machine.prototype.begins = function (input) {
		this.current = this.states[0];
		this.advance(input);
	};
	
	
var json = new Machine();
json.verbose = true;
json.define([
	{
		name: 'parse',
		action: function (input, next) {
			input.foo = 'not bar';
			next(input);
		},
		to: 'stringify'
	},
	{
		name: 'stringify',
		action: function (input, next) {
			next(JSON.stringify(input));
		},
		to: 'done'
	},
	{
		name: 'done',
		action: function (input) {
			console.log(input);
		}
	}
]).begins({
	foo: 'bar',
	apple: 'orange'
});

json.add({
	name: 'wrap',
	before: 'done', 
	action: function (input, next) {
		next('<em>' + input + '</em>');
	}
}).begins({
	foo: 'bar',
	apple: 'orange'
});