Turnpike

A minimal finite-state machine for JavaScript.

Installation

$ npm install turnpike-sm --save

Usage

const Turnpike = require('turnpike');

const turnpike = new Turnpike(initialState, transitions, options);

initialState and transitions are required. The first is the initial state for the state machine to start in, the second is an array of transitions that will happen when a given action (name) occurs;

const turnpike = new Turnpike('asleep', [
  { name: 'bother', from: 'asleep', to: 'awake' },
  { name: 'bother', from: 'awake', to: 'bothered' },
  { name: 'rest', from: 'jumping', to: 'asleep' },
  { name: 'jump', from: Turnpike.ANY, to: 'jumping' }
]);

The special value Turnpike.ANY will match any from state.

The third argument (opts) currently accepts 1 option: opts.EventEmitter is an alternative EventEmitter implementation to use, if your platform doesn't include node's require('events').

instance methods include:

turnpike.act(actionName, [...args])   // Perform an action
turnpike.getState()                   // Retrieve the current state

Turnpike includes an EventEmitter and provides several events on each state transition:

turnpike.on('exit:asleep', (...args) => {
  console.log('Sleep over', args);
});

turnpike.on('exit', (stateName, ...args) => {
  console.log(`Exiting ${stateName} with args:`, args);
});

turnpike.on('enter', (stateName, ...args) => {
  console.log(`Entering ${stateName} with args:`, args);
});

turnpike.on('enter:jumping', (height, speed) => {
  console.log(`Started jumping, height: ${height}, speed: ${speed}`);
});

turnpike.act('jump', 12, 'fast');

Testing / Linting

$ npm test
$ npm run lint

Migrating from 0.x to 1.x

A few minor breaking changes:

• Initial state is now a separate argument.
• ev was renamed to name in the event definition.
• Now uses EventEmitter syntax (on('event', ...)) rather than bespoke onEnter / onExit handlers.
• No more browser build provided - you should be bundling that yourself.

License

MIT